Civic VX Emissions Failure - VTEC Malfunction, or Hopelessly Epic Melodrama?
 

Hey everybody. Firstly, this is my first post here, and I just wanted to acknowledge how amazing this community is. I discovered the Civic VX from this site a year ago, and managed to find one that was in very good well maintained and surprisingly unmolested condition, with 182,000 miles on it. This 1993 Honda Civic VX was and is my first car.

Recently, I moved to California. For the last 3 weeks or so, I have been trying to get it to pass the emissions test here, in order to get it registered. Here is the emission test results:

https://jedypod.com/media/photo/emiss...st_results.jpg

I am not the most mechanically godlike person, however, I am good at learning about things. When my car first failed, I did a bunch of reading on various forums, and a whole bunch of learning about how my engine works (helped greatly by all of the awesome information on this site!)

My Story:
The first thing I tried was to check and change the spark plugs. I bought a set of NGK ZFR4F-11, and replaced the ZFR5F-11 plugs that were in the car. The plugs were clean, no carbon buildup, and no excess fuel present. The tip ceramic was slightly pink. I took it back to get re-tested, and there was no change.

There is an intermittent check engine light that comes on, usually when the car is run at higher rpms for a period of time, or when it is under heavy load. For example, accelerating in 3rd gear at 3000+ rpm for 20 seconds or more going onto the freeway can trigger it. I read the CEL error code and it is a code 22, which indicates a failure of the oil pressure switch in the spool valve assembly. I troubleshot it to the best of my ability with the troubleshooting diagnostic procedures in the Honda Civic 92-95 Service Manual, not being able to test the oil pressure without "special tools".

Desperate and sad, I added 22ml of Acetone to the 3 gallons left in my gas tank, and took it in for another re-test. (I had read reports of using Acetone as an fuel additive reducing HC emissions by up to 60% and thought I would give it a try). There was no change in the test.

Finally, I decided that this problem was beyond my capabilities, and even in my desperate poverty, I took it to a well-regarded automotive smog shop that is a gold-certified smog repair facility (emissions testing laws in California are intense and complicated).

2 days later, I got a call back essentially saying "your car is confusing and we couldn't fix the problem, but we won't charge you money." I talked to the mechanic who worked on it, and it soon became apparent that I knew about as much about my engine as he did. He guessed that the problem was the VTEC engaging too soon, because of the extremely different %O2 readings between 15mph and 25mph. He said that the VTEC shouldn't engage until 3000 rpm. While I think the value is supposed to be somewhere around 2600 for the VX, and depends on a bunch of factors like gear, throttle, fuel-air mixture, and various other incomprehensible things, there is probably some truth to his diagnostic. They also said that the Catalytic converter was likely slightly depleted, because of the higher than average NOx readings, but that it should still be good, and it would not account for the extremely high HC readings at 25mph. They recommended that I take it to the dealer to get the VTEC mechanism troubleshot.

They said that they tested all of the obvious things, that is, ignition timing, O2 (LAF) sensor, tested for vacuum leaks, and so forth, and that everything checked out fine.

I have a vague memory of the guy I bought the car from telling me that he "adjusted the vtec down to 2300, which is where it is supposed to be". From what I have read, it seems that if you adjust the "VTEC Crossover Point" without calibrating fuel maps and timing (I don't really understand this well enough to talk about yet), it will seriously throw off the engine's tuning, and it can end up with the ECU telling the injectors to squirt way more fuel into the combustion chamber that can be burned, resulting in an overly rich mixture, which could result in a high HC failure in the emissions test.

The car itself runs fine. It gets between 36 to 44 miles per gallon (my best tank is 45 on freeway driving). There is a slight hesitation in acceleration that is noticeable sometimes at around 2200 rpm. It is very slight and ... non-violent, so I assumed this was related to the VTEC mechanism engaging. The car idles at about 1200 rpm when started cold, and eventually equalizes to about 900 rpm. Sometimes, after driving for a while, the idle will drop all the way to 400-500, but it never idles rough, or stalls. The engine burns about a quart of oil every 1000 miles.

With this evidence presented then, my question for you, kind compatriots of fuel economy questing, is:
How do I adjust the VTEC engagement point, and is this even possible? And more generally, what advice can you give me from your collectively vast VX VTEC-E knowledge that might help me pay less money to get my fabulous car to pass emissions?

Thank you greatly in advance, and I apologize for writing a novel on my first post! ;\

Interesting. Is it possible to contact the previous owner and ask how he adjusted it? There may be several ways to adjust the vtec engagement.

Burning oil can't be good, and may be related to the code it's throwing. It's possible that the burning oil is the cause of your HC readings, though my first guess would be a rich fuel mixture.

Thanks for the reply, theholycow. I have sent the previous owner an email, however I have not received a reply from him yet. I bought the car from him a year ago, so it might be a dubious endeavor getting a reply from him.

Do you know what the several ways that VTEC engagement might be adjusted are?

What might be causing my oil to be burning, thus producing high HC readings? I have heard that faulty head gaskets results in oil leaking into the combustion chamber, and that this results in blackish smoke coming from the exhaust when running. There is some smoke that is visible when accelerating violently, but under normal conditions the engine produces no visible exhaust. I assume a leaking head gasket would produce other more noticeable symptoms as well.

Thanks for your help!

If the head gasket is leaky, more likely it will burn coolant, not oil. If it burns oil I would suspect the valve guides, seals, and/or piston rings are to blame. None of which would be easy to replace.

Usually the way the vtec engagement is changed is by swapping in an ECU that can be hacked though the use of a non-honda program, all of which would make the car fail emissions testing if the car was not tuned properly. I have not heard of anyone being able to hack the VX ECU so if the wrong ECU is installed, you need to swap in the correct one. I know there is some helpful link on this site to check to make sure you have the correct ECU installed by checking out the numbers on it. Other than that the previous owner could have installed a Vtec Controller which is basically a hack into the engine's wiring and in no way helps performance.

The VX ECU does engage vtec at a lower RPM than any other honda vtec system so your mechanic being surprised does not surprise me, since this is a strange motor for most mechanics to look at and try to understand without some advanced reading into how it works, or at least a glance into the VX shop manual.

Definitely check which ECU you're running. It should be under a cover in passenger side footwell, just forward of the door. There should be a label on it with a bar code and a couple of numbers. One of them should be in the form of #####-###-###. The last six digits of that number can tell you which engine the ECU was meant for, which emissions specification (cali, federal, high altitude, ect.) and which revision it is.

Similarly, look at the front of the engine where it meets the transmission. There should be a raised square cast into the block there. It may be covered with grime, but there are engine model and serial numbers stamped into that square. The model should be D15Z1, but engine swaps are pretty common so check to be sure.

Remove the spark plugs and lay them down in order (so you know which plug came from which cylinder) and compare the color of the electrodes. They should have a light tan color with very little variation from cylinder to cylinder.

So I checked my ECU, and indeed it appears to be the correct Federal VX model. The number on my ECU is 37820-P07-A00-670-111097, which is consistent with the characteristic VX model listed here.

My engine definitely is a D15Z1, as it was one of the first things I checked before I bought the car! ;P It has D15Z1 stamped on it.

I have looked around in my engine, and although I'm no expert, I don't see any vtec-controller type modifications that look like they are tapping into the wiring that goes to the VTEC Spool Valve Assembly.

Page 5-7 on the USDM 92-95 Civic manual mentioned in my first post explains that the Variable Valve Timing and Lift Electronic Control System (This is what VTEC Stands for! I think) crossover point is controlled by the ECU based on a number of different variables, and should engage between 2500 and 3200 rpm, depending on these variables. The explanation is as follows:
https://www.fuelly.com/attachments/fo...2f1bb18f48.jpg

So since the RPM that the HC failure in the test occurs is around 2300, which is under 2500, the engine should still be in lean-burn mode, unless something is messed up. The question is, what is messed up, and how to fix it? I wish I understood this better!

The sparkplugs that I took out of the engine looked pretty clean, and consistent from cylinder to cylinder, as far as I could tell. Here is a picture of them.
https://www.fuelly.com/attachments/fo...5f995af83a.jpg
Same order, rotated slightly:
https://www.fuelly.com/attachments/fo...56d773d43e.jpg
#4 on the right seems to be slightly more dirty... but is this really enough to indicate a problem?

Thanks for your helpful comments!

The plugs look pretty good compared to the plugs that have come out of my VX motors. I don't think any of them look significantly bad enough to show a problem exists.

Good luck getting it to pass the smog, wish I could be of more help.

Yeah, those look fine. A lot like the ones in my 'Z6 (I had them out a few days ago).

Well, I'm going to say fix the diagnostic code before diving into other stuff. The ECU can behave strangely when it's trying to compensate for a perceived failure.
Looking at the pressure switch diagnostic procedure, it has you check the wiring first, then go on to oil pressure/switch tests. Like you said, you need some extra hardware to do those tests, so I say skip them. Instead, look at the results of those tests: Either inspect the spool valve, replace the pressure switch or replace the ECU. I would inspect the valve first (p. 6-23) since it only requires maybe half an hour with a multimeter and a metric socket set. If the valve seems to be fine, replace the switch. If that doesn't fix the code, try a known-good ECU.

So I did some troubleshooting to the spool valve and oil-pressure switch mechanisms. Not having the equipment for the oil pressure tests, I tested all the electrical continuity stuff that I could, according to the VTEC Troubleshooting instructions on 6-18 to 6-22. Everything seems as it should be.
Following the directions on 6-23, I inspected the spool valve. The resistance between the 1P connector and chassis ground is about 16 ohms, which is right within the specified 14-30. I took apart the spool valve assembly, and checked the Spool Valve filter and the filter behind the oil pressure switch. It all looks clean, and appears to be functioning normally. The movement of the spool valve itself also appears to be working properly.

I decided to check the engine error code again, just for the hell of it, and realized that you are supposed to reset the ECU after reading the error code, which I hadn't done before. So, I look in the under-hood fuse box (for the first time), and I discover that the BACK UP fuse (7.5A) is blown. I replaced the BACK UP fuse with a spare 7.5A fuse from the other fuse panel, and drove the car for a minute, and it didn't blow again.

Could this blown fuse have been messing up the ECU's function? Or perhaps could it have been causing the problem in some other way? Maybe it's nothing, but it does seem a bit suspicious to me. Any thoughts on this new development would be appreciated!

Thanks so much for your help, once again! :)

Wow, that's strange. Yeah, if the back up fuse were blown, the ECU could have been resetting itself every time you turn the car off. Or Something... The ECU reset procedure calls for putting the fuse back in place when you're done. I'm not sure if the ECU would behave in a predictable manner if you fired it up with no power on the memory backup circuit at all. You had properly stored (persistent between resets) error codes, right? As in if you turned the ignition off and back on, the ECU would still display codes from a previous CEL event when you jumped the service connector?

The intermittent Check Engine Light that I was getting for the Spool Valve Oil Pressure Switch would go away whenever you turned off the ignition. That is, say if I went for a drive, and accelerated hard to get up to speed on a freeway, and the check engine light came on. If when I got home, and I jumpered the service connector, and then turned the engine off, and then turned the ignition back to ACC, it would blink the error code. However, if I just turned the car off, and came back the next day, it wouldn't blink the error code from the previous day. This makes sense, I guess, because the Back Up Fuse was basically not there, because it was blown.

I remember reading somewhere that the ECU stores a history of the driving performance, or something, and bases its operations on that somewhat. (some guy was saying on a forum that he took his recently reset ECU in his car to get his emissions checked and they said he had to come back, or something). Is that even remotely factual?

Hmm... this is perplexing. I wish there were some way to test to see if it this changed the engine's fuel mixture at all without taking it in to get smog-checked again.

Well, I can't say for sure, but I failed emissions once because I forgot to remove the jumper from the service check connector. This was back when I was still running stock-ish OBD-0 engines/ECUs, which have no indicator that it's in service mode beyond the jumper itself.

Yes, I've read that some ECUs use cumulative fuel trim functions... OBD-2 ECUs definitely do, OBD-0 definitely do not. I'm not sure about OBD-1, but I'm leaning toward do... The fed. emissions VX ECU in particular with its additional processor and wide-band sensor.

Just a thought...could it be that the catalytic converter is just plain worn out?

As for the mechanic being confused, that seems to be a common problem. When I take a car to a mechanic (a rare situation, usually happened when I was commuting 200 miles a day and working 70 hours a week, back in my former life as a retail store manager), about half the time I have to fix their "repair" so the car will run right.

It is my understanding that the catalytic converter affects CO and NOx levels more than hydrocarbons. While those levels indicate that my Catalytic converter is relatively depleted, it still has enough life in it to pass the emissions test.

The failure is being caused only by abnormally high HC emissions only in 2nd gear at ~2300 rpm. This, along with the greatly changed %O2 and %CO2 readings indicate that the fuel mixture is changing drastically on the 25mph portion of the test, most likely because the VTEC is engaging.

But as for your comment about mechanics, I am definitely being very cautious, and saying "I have a VX, the only Honda with this particular VTEC-E engine sold in the USA. Are you sure you know how to fix it?". Mechanics are extremely optimistic before they get your money, I have discovered. I am also being very careful to find out exactly what things they do to the car.

I am taking it to another place tomorrow, which will hopefully have enough knowledge to troubleshoot the VTEC system's functioning and proper tuning.

Thanks for your comment!

If it's only happening in 2nd gear...I wonder if you could hack in a 2nd gear lockout and stick a label on your shifter with a new shift pattern? You won't be fooling the guy doing the inspection, but you'll give him the excuses he needs to pass you; he'd be driving the car as you've modified it...

It's not like you cruise around in 2nd gear at 2300 RPM, so it's not like you'll be pumping out an inappropriate volume of pollution.

Do you have a shop manual for your car, or barring that, a Haynes manual? (Don't get the large Chilton manual if you can help it, the information will probably be in there, but it'll take you hours to find it!)

Hi,
I believe that the manual I linked to in my first post is the "official" shop manual. If you know this not to be the case, please correct me, and if you could, point me to the correct service/shop manual for for the Civic VX, if it exists on the internet.


One of my first ideas was to just ask the Smog Technician to run the 25mph test in 1st gear, but when asked about that, they informed me that the RPMs for the test had to be between 2000-3000 rpm. Needless to say, with the VX transmissions, 1st gear @ 25mph is about 4000 rpm, and 3rd gear @ 25mph would be lugging the engine pretty significantly.

By 2nd Gear Lockout, you just mean essentially disabling 2nd gear right?

If they do 25mph per the dyno and not per the speedo, just borrow some bigger wheels/tires to put on the front.

Yes, that's exactly what I meant.

I just ran the numbers into a gear calculator and there's no way you're getting either 1st or 3rd into the 2000-3000 range for the test, but the point of my idea was to change your RPM.

RW's idea of using a different tire size might work; it will change the RPM of your engine at 25 if the speed is measured at the dyno, or the load if the speed is measured on your speedometer...either one of which may change the emissions.

Here is the latest update in my epic sad tale of Civic VX emissions malfunction.

I took my car another mechanic shop that turned out to be a lot more competent with Honda engines than the previous place. They informed me of the following discoveries:
(this is the description of the problems I got on the invoice): "Lab Service - Diagnose for smog failure. Technician found no oil pressure to VTEC Solenoid even with power applied to it, EGR solenoid not ground by ECM, which cause higher NOX emission. Also notice cylinder head had been drill where VTEC solenoid go. Need new ECM and cylinder head tear down for further inspection since head gasket had been replaced."

So the spool valve (VTEC Solenoid) has no oil pressure, which is resulting in the VTEC mechanism not engaging. The Code 22 that the ECU is throwing every time I rev the engine under load is being thrown because the VTEC is trying to engage, and is not able to. The guy said he tested the spool valve and the oil pressure switch, and both are mechanically and electrically functional, and the screens are not clogged or obstructed (as I established when troubleshooting the problem myself). However, he says that they even tested the spool valve under load, and only a dribble of oil was coming out, where there should have been at least 57 psi.

The head gasket was replaced by Chevron Nisqually Automotive and Towing @ 132,000 miles (the car has 190,000 now). The tech thinks that they may have put the wrong head gasket in the engine, which might be missing the holes necessary for oil to get to the VTEC Solenoid, causing there to be no oil pressure there.

Additionally, the EGR Valves are not functioning as they should. The tech says that this is being caused by the ECU controller, and not by any fault with the valves themselves, or the wiring to the valves. He says a new ECU is necessary to fix that. He says that these problems are causing the engine to misfire, resulting in high NOx and high HC emissions levels.

He also mentioned something about a hole being drilled or enlarged in the cylinder head underneath the spool valve assembly. I have no idea what this is about... but it frightens me.

Even with all of these things wrong with the engine, I have still been getting around 40 MPG in mixed driving. I am excited to find out just how much better the car will drive when it is running properly! I am also kicking myself for paying as much as I did for the car, and for not finding out what was wrong with it from the seller (who I am pretty sure purposefully put a blown fuse in the ECU Reset fuse holder). I guess next time I buy a VX, I will know exactly what to look for.

So my plan (since I am poor, and can't afford to pay 800 dollars to have a mechanic take apart my engine and replace the head gasket) is to attempt to do it myself. My Dad (who lives nearby) has all the necessary tools, and a fair amount of experience with engines, and I think that this combined with a healthy amount of research into online tutorials, and having a couple shop manuals on hand will be enough for us to do it without breaking anything.

And I guess I am also in the market for a VX Federal ECU (P07-A00 [manual transmission] or P07-A01 [auto transmission, should still work with my manual trans, right?]), if anyone has one that they want to sell.

OK, I missed the link you had in your post.

If you can have your dad mentor you through the project, then all should be well.

Might not hurt to have a competent machine shop look at the head while it is off...check the valves, etc.

How are the rings and bearings? Since you are getting that far into the engine anyway...

If you go to a junkyard to get a replacement ECU, and they offer a warranty for it, it might not be a bad idea to go for it.

car-part.com lists junkyards with that ECU for $60 to $175. Chose "Computer box-engine" from the list, they don't list "ECU".

One month later, here is an update on the latest developments.

Electronic Control Unit - Exhaust Gas Recirculation Fixation
As I mentioned in my last post, the mechanic I took the car to told me that the EGR valves were not functioning properly, because of an ECU failure. I bought a replacement P07 ECU on ebay which was supposedly tested and fully functional for $80. Before swapping the ECU out, I went through the EGR valve troubleshooting steps on 11-34 to 11-39 of the 92-95 Civic Repair Manual, and indeed the EGR was not grounded properly. After swapping the ECU with its replacement, the same test indicated that it was now grounded properly. I took it back to get its emissions tested again, and the results were not that great. The NOx emissions were improved slightly (closer to 200, down from 300-800). The HC emissions at 25mph was improved slightly also, but still over limits. The lowest PPM measured was 92 at 25mph, and the max allowed to pass is 62.

Head Gasket Replacement
So my dad and myself went forward with the head gasket replacement plan. As I said above, the mechanic indicated that there was no oil pressure at the Spool Valve assembly, and that this was why the VTEC system was not engaging properly, and the reason for the CEL Code 22 (Oil Pressure Switch) coming on when engine conditions would normally result in VTEC crossover, if everything were working properly. The mechanic thought that the reason for the lack of oil pressure might be because of an improper head gasket being previously installed, resulting in oil being blocked from coming through passages that it needed to, in order to get to the Spool Valve Assembly. This always seemed a little far fetched to me, but we went ahead with the investigation.

So armed with an empty day in front of us, and a box of tools (10mm, 12mm, 14mm wrenches and sockets, torque wrench for torquing down the head bolts again, some pliers and wrenches and so forth), we started tearing apart my engine. I will include some pictures by way of visual explanation, as other people might find it useful.

We roughly followed the instructions for Cylinder Head Removal starting on page 6-28, and Cylinder Head Installation, starting on page 6-53 of the Repair Manual. We disconnected all hoses and electrical connections to the head. We drained the coolant (the engine coolant drain under the exhaust manifold was seized, so we had to use the radiator drain, and the lowest coolant hose going into the engine block to drain the coolant to a level below the head gasket. This ended up working fine.)

We removed the Timing Belt cover, and the valve cover, and set the Cam Pulley so that the "UP" mark was straight up, so that the first piston was at Top Dead Center. We were able to turn the engine over with just a wrench on the Cam Pulley retaining bolt, but we ended up moving it into position by putting the car into gear and rolling backward (reverse moves the cam pulley counter-clockwise, 1st or 2nd, clockwise). The Cylinder Head Removal instructions in the repair manual tell you to remove the timing belt completely, but my dad thought we could mark the exact position it was in, and just remove the Cam Pulley section of the belt, thus saving ourselves some work. This actually was successful. Here is a picture of what we did.
https://www.fuelly.com/attachments/fo...6e15ea5c3a.jpg
It looks pretty bad, but it actually worked okay. First we marked the Timing belt with Duct Tape in the exact positions of the 9:00 and 3:00 marks (using the "UP" mark as 12:00). This was accurate enough to put it back in the exact same divets. We unbolted the Cam Pulley, and pulled it out, while simultaneously sliding the timing belt back towards the block. Using two sets of hands, we kept upward pressure on the timing belt as we removed the pulley. We then had to figure out a way to lock it in place, so that it wouldn't get loose and slip on the Belt Tensioner or Drive Pulley. We used an available thing, and jammed it gently into the right side, which kept it from slipping back, and then another available thing on the other side, folding over (but not crimping) the slack at the top. This held it there.

We removed the Head Bolts in the order specified so as to not warp the head, and kept them in order. Note that removing the valves is not necessary for the removal of the head block.
https://www.fuelly.com/attachments/fo...5168f8d514.jpg
This is the engine with the head removed... The cylinders don't seem too worn, as indicated by the lack of a ridge around the top, according to my dad.
https://www.fuelly.com/attachments/fo...54d2071558.jpg

To my great lack of surprise, the head gasket was the correct type for the engine, being exactly matched to the replacement that I bought.
https://www.fuelly.com/attachments/fo...9a201db7dc.jpg
https://www.fuelly.com/attachments/fo...6d41aa29d1.jpg
Here is the bottom of the head, displaying all of the holes in their correct locations. We were somewhat disheartened by this discovery, but at least we ruled it out as a cause of the VTEC problem.

We spent a while investigating the oil passages going to and from the Spool Valve Assembly, using a small air compressor to establish flow destination.
https://www.fuelly.com/attachments/fo...65d831ca98.jpg
You can see the oil passageways that go into the Spool Valve Assembly at the right of this picture. The middle passage (2nd from the bottom) is the main input port. Oil comes up through an internal passageway from the input port that I assume comes up from the main oil reservoir. (this passageway goes past on the inside where the red allen wrench is stuck in there).
https://www.fuelly.com/attachments/fo...d9b3adacd9.jpg
This passageway is visible here, as the little nipple looking thing in the center on the rear between pistons 2 and 3.

The passage third from the bottom goes into the rod above the camshaft that the valve rocker arms are attached to. I think this is where oil pressure goes in order to switch the VTEC on and engage the higher cam profile. We reasoned that the function of the Spool Valve Assembly was to switch between allowing and disallowing high oil pressure to get into this passageway.

I can't remember where the bottom passageway went.

The real interesting passageway though is the top passageway, which as you can see goes directly into the valve chamber on top of the head.

We re-assembled the engine with the new head and manifold gaskets, and after everything was in place except for the valve cover, we started the engine. It started right up, but after a second, my dad noticed oil starting to pour out of that top hole in the Spool Valve Assembly into the valve chamber. He thought this to be very odd, thinking that oil was going to be coming out of the tube that the rocker arms attach to, in order to lubricate them.

We immediately turned off the engine and investigated to make sure everything was on correctly and that we hadn't forgot anything. It was, and we hadn't.


A Question About Oil Flow
The mechanic was babbling on about how someone drilled a hole in the head near the spool valve assembly. At the time, I was just very confused, but I am wondering if this hole that goes from the top chamber of the Spool Valve Assembly into the Valve chamber on the top of the head block might not supposed to be there? Has anyone here seen the inside of a D15Z1 head block, and might they be able to tell me if that hole is supposed to be there? I can't seem to find any oil flow information on the engine. What do you all think?


Valve Adjustment
After the head was back on (and before we started the engine), we adjusted the valves. Interestingly enough, many of them were very tight.

I had adjusted them with a friend soon after buying the car, in order to see if the strange clicking sound that the car makes when in gear and accelerating (but not decelerating), and only when the car is started cold, was being caused by the valve lash being loose.

My friend had tightened them a bit too much, I think, because all of the valves were tight, and the exhaust valves on two different cylinders were almost 3/4 of a turn tight.

I'm not sure if the problem of tight valve lash would be enough to make the engine misfire and run rough enough to fail emissions, but the engine definitely feels like it runs smoother now. Before there was a rhythmic hesitation in the engine as it idled (very subtle, but noticeable), which is gone now.

Tightened valves still doesn't explain the abnormally elevated HC levels on the 25mph portion of the emissions test but not the 15mph portion... does it?

I am wondering if I should go back and get it retested again to see if the valve issue helped at all.

If the valve lash was adjusted too tight, some of the valves may not have been closing all the way once the engine has warmed up fully. Who knows what that would do to the combustion process.
Also, valves rely on closing fully to cool properly. Contact with the seat on the cylinder head lets heat conduct away, rather than being forced to travel all the way up the stem to the valve guide. Overheated valves can warp and crack... Maybe you already did (too lazy to scroll up), but I would do a compression test to make sure everything is as it should be.

Where does the oil from your suspicious hole go in the cylinder head? Does it just run over to the nearest drain, or does it fill the galley under the camshaft or something? My copy of the '92 service manual appears to show a hole there on page 6-23 (spool valve inspection). Take a close look at the diagram that shows the valve, filter/gasket and mating flange on the cylinder head, as well as a mounting bolt with torque spec.
[edit]
Check out page 6-67 "Inspection Using Special Tools". I believe that relief hole is the one you're worried about.
[/edit]

One more thing... You're dealing with a D15Z1 block, right? That nipple thing on the block has a pretty big hole in it? Non-VTEC engines use a restrictor there to control oil flow into the cylinder head... That restrictor has to be drilled out or completely removed if a VTEC head is installed on a non-VTEC block.

Hi Bobski, thanks for the thoughts. You are definitely right about the Relief Hole being a hole with a legitimate existence. It looks like I missed that the first time around. It does definitely look like it is supposed to be there. The oil from it just seems to pool up at the bottom of the ... "valve chamber" just the space inside the valve cover, underneath the valve rocker arms and the camshaft and so forth. The excess seems to flow back into the oil ports, and get splashed around by the valve action. We weren't able to run the engine very long with the valve cover off, because the oil started to overflow over the edge near the spool valve.

Upon a pretty close visual inspection, the valves seem to look fine, but we will definitely do a compression test and see what we find out before bringing it back for yet another emissions test. If I am lucky, maybe the main remaining contributing factor causing emissions failure was the over-tightened valve-lash, and it will pass now.

The cylinder block has D15Z1 stamped on the outside of it, and there is nothing to indicate that the head is of a different model, so I am assuming that they are both of original stock origin. You can get a pretty good idea of the "oil nipple" size in the 3rd picture down in my last post. If I remember correctly, the size of the hole doesn't change from the exterior surface as it goes down.

Yes, I'd go back and get it retested. Sounds like your valves might have been just barely not closing, which would cause it to not run quite right, and would have burnt your exhaust valves in short order.

Did you adjust the valves when the engine was cold? Does your book give two specs for the valves, one for cold and one for warm engine?

One of my dad's pieces of wisdom he passed along to me was "If you hear the valves ticking, you KNOW they are closing". I've usually tried to get them as close to spec as possible, but at least I don't worry if there is a little ticking.

BTW, really nice pictures.

Here is another update.

The compression test yielded no problem indications, in fact it tested very well for an engine with 190k miles on it. Each cylinder tested within 5psi of 200psi. The optimal number is 185psi ?20 for the D15Z1, if I remember correctly. ( this was tested with the ECU fuse in the under-hood fuse box unplugged, so that the injectors didn't spray fuel into the chamber, and with the throttle fully depressed, while cranking over the engine ).

I went back to get the car tested, allowing myself to raise my hopes slightly, and this is what I get:
https://www.noelshack.com/up/aac/emis...145da67119.jpg

Even worse emissions than before I did any repairs, in the NOx section, and slightly lower on the number that is making me fail -- the HC @ 25mph.

I took the car in to get it tested before we took the engine apart and replaced the head gasket, and adjusted the valves also. They didn't do an official test, but just ran it for a minute and gave me the numbers (for free). On this test, the HC was about the same as the above results, and the NOx were about 150 points lower on each.

This means that tearing the engine apart and adjusting the valves had no positive effect on the emissions results. However, replacing the ECU had an effect, bringing the HC @25mph down about 25 points.

Interesting, no?

I reason that the next thing to check off the possibilities list is the Catalytic Converter, since from what I hear, that device is also responsible for reducing HC, and maybe the engine running with an EGR that was not grounded properly by the previous faulty ECU caused the emissions to clog up the catalyst surfaces. ( this seems a long shot, given the un-changed emissions results pre and post EGR fixing (hopefully it is fixed?)).

I was going to take it to a muffler shop nearby to get it replaced tomorrow, when I happened across this thread, wherein suspendedhatch says
This makes me think that the muffler shop I'm going to probably doesn't have the proper Catalytic Converter in stock for my car like he thinks he does.

The OEM Catalytic Converter for the VX is only available from Honda...trust me I've searched all my parts connections. And it's not cheap, about $400+ last I checked.

You can go with THIS Maniverter for the 96-00 Civics and have your muffler shop install it.

Another option is to go with an aftermarket ebay header for around $40 and then get the regular catalytic converter for a Civic Si and have the shop install that. That option requires more fabrication than going with the 96-00 maniverter though.

RockAuto.com has one from Eastern Catalytic Converters (#40352) for $285.99 and one from Bosal (#099249) for $364.79. Unfortunately, those are both non-CA emissions cats (there's a difference?), so they won't ship to CA.

Walker claims that they have a replacement as well, I've ordered it before and it's nothing more than a regular catalytic converter. It's frustrating that most aftermarket parts companies don't know that the VX is different.

It is good to see that the pic referenced on the RockAuto site does look correct.

It has also been three years since I've personally looked for a VX specific CAt too.

Thanks for the tips, again, guys.

Sure enough, the guy at the Muffler shop didn't realize that the VX had a manifold-mount catalytic converter, and he didn't have on in stock, and doesn't know of any place to order one. He suggested I go to the Honda Dealer.

I called up the dealership, and sure enough, they charge $626 for a new catalytic converter for the VX. I tried to get them to tell me what the difference was between a "California" model, and a non-CA model, but all I could get out of them was "Honda does not sell illegal parts, and this Catalytic converter will be made for your car."

So I also am very curious what exactly the difference is between CA and non-CA model Cats.

If the model on RockAuto (which looks right to fit my car) will fit, and is built to OE specifications, I don't really see how it would be much different than the dealer one. Maybe I will drive out of state to install one or something.

Assuming that my catalytic converter is actually depleted, which is supposed to never happen. Do you guys think there is any possibility of the EGR being (in theory) non-functional causing the CAT to become clogged up? Maybe I should take my cat off and take a look inside.

They don't get depleted as in the catalyst wears out or blows away or something. They get depleted when the catalyst gets poisoned by trace heavy metals or coated by some other stray material. And of course, there's clogged cats, either by carbon or by damaged catalyst structure. Clogged cats are generally pretty easy to diagnose since they will heat up red-hot when the engine is under load.

The EGR system reduces NOX emissions by reducing combustion chamber temperatures. The exhaust (an effectively inert gas) is metered into the intake stream where it displaces some of the air/fuel mixture that would have otherwise burned in the cylinder. Less stuff burning means lower temperatures.
Looking at those numbers, I think you're getting incomplete combustion of some sort. You've got both excess hydrocarbons and oxygen in the exhaust stream. You're sure your cam and ignition timing is set right? The proper heat range plugs? I guess if the EGR valve was stuck open, it could cause combustion issues.

Wouldn't hurt.

Maybe 1 or 2 EGR runners in the intake manifold are plugged with carbon and all the EGR is going to one or two cylinders causing them to misfire at times (incomplete combustion).

Interesting theory. I don't have a EGR-equipped manifold to look at for myself... Is the exhaust gas distributed to individual runners by a sub-manifold, or is it fed in collectively near the throttle body like the evap. gasses?

Not sure- here's a thread https://www.gassavers.org/showthread.php?t=8721

Yeah, ok... looks like a sub-manifold / distribution rail setup to me.

Smog problems
 

Although I have yet to get my VX smogged here in California. I have had to get a lot of high mileage Japanese cars smogged and I have discovered a couple of things. At around 200,000 miles it becomes very difficult to get these cars to pass because the catyltic convrter is warn out (contaminated, whatever). I managed to get my 87 CVCC civic to pass twice (got through 4 years of checks), after an initial HC failure by doing a tune up (plugs, wires, cap, etc) and (the most important point) setting the timing back as much as possible (same story on a Miata I had). I think the range is 16-20 BTDC on the VX, so set it to 16 or (15 degrees if you think the smog tech will let you). Also you want the cat as hot as possible, but the air temp not so hot (not a 100 plus degree day). However, this method will only get you about a 10% drop. So this probably wont be enough to get you to pass.

Last year, after 6 years of barely passing, I couldnt get the 87 Civic to pass, so I had to go to plan B, which is a new cat. This was an easy fix until 2009: You go to any muffler shop and they weld in a second, cheap cat under the car (after the first one for anywhere from $50-$100, and presto the car passed. From what I understand, the cats are cheap and probably burn up before your next check in two years, but who cares.

Anyway, thanks to a new law here in California as of 2009, it is no longer enough to meet the emissions test. To be sold in CA your new cat has to be in the same location as the original. For OBDII cars, it has to be on a CARB list. See the following website: https://www.car-sound.com/04basics/04california.asp . What this means is, basically, that the cat manufacturer has to get a carb number for their cat on your particular model. Since this is California only, most of the replacement cat manufacturers simply wont bother with selling to Ca. (It could be that the 49 state cat is a perfect replacement in terms of form, fit, and function, emmissions, etc but no CARB EO number means its illegal to sell in CA.) The big names, like magnaflow and Walker will sell here, but since only the VX and CX used the manifold mount cat, there isnt enough market to bother making it. So you either have to go out of state for a $75 second cat or step up to a $450 Honda replacement (which we are lucky Honda even still offers). Used factory cats can be found on craigslist (although its probably technically illegal to buy one), but maybe that used cat has even more miles than yours, so its a gamble. Junk yards havent sold used cats here in a long time.

The only other VX speciffic tip I have is to install a CA ECU (is your ECU PN 37820-P07-LXX? If so its a CA ECU and will never go into lean burn) which will lower your NOX emmissions. NOX emmissions in lean burn mode is the whole reason the CA model got its own ECU in the first place. Its a 5 minute swap and everything works great but you loose lean burn and the shift light (at least on my 92VX). Since your NOX is passing, this probably wont help. Also, regarding cleaning the EGR passage, this would improve your NOX, but your NOX is OK, so I wouldnt bother. Id be willing to bet money that a new cat will solve all your problems. You can try a tune up and retarding the timing, but I dont think you will quite get there.

Good luck. Let us know how it goes.

So I also am very curious what exactly the difference is between CA and non-CA model Cats.


As far as factory Honda parts go, there is no difference between a CA and non-CA cat. They are the same part number (18160-P07-A00). For aftermarket manufacturers, the difference is whether or not they want to bother with a CARB certification - the difference is in the paperwork, not the hardware.

Unfortunately, I think Honda is the only source for a cat that mounts in the factory location. The CX and VX were made in too limited a number for the aftermarket to bother.

I know for a fact that Magnaflow listed the wrong cat for the VX in its catalog at least as of last year. When Summit Racing delivered it, it was a for an Si/EX 1.6 VTEC. It was a nice piece and under $100 I think, but would only bolt to a 1.6 manifold and exhaust pipe.

Edit: That Rockauto part looks like a bolt in replacement. The only difference I see is that the factory heat shield wont bolt around the cat, so it will look different, which might or might not be a problem depending on the kind of smog tech you get (but shouldnt be). (Just be sure it is a three way converter - CO, NOX, HC - and not a two way - but I dont think they make two way converters anymore.)

I did try a "bolt on" aftermarket replacement for my 87 Civic last year when you could still buy them, and it was pretty close to the factory part, but the angle of the flange was off by a couple of degrees and the down pipe ran into the oil pan. My guess is that the quality control was off, so a different one would have worked fine, but that particular one didnt fit so it went back to Kragen (and I was kind of in a bad mood at that point as taking apart and reinstalling rusty 20 year old exhaust bolts without snapping the bolts in half is not fun). The rockauto part SHOULD fit, if you can somehow get it delivered, but make sure they have a good return policy if the part doesnt fit.

Awesome, thanks for all of the ideas, especially the Catalytic Converter info, caccox.

Today, I removed my catalytic converter to take a peek inside, in order to determine if it were melted or covered with extreme carbon deposits or fractured (as pictured here).

To my great lack of surprise, it looked fine. This means my engine is not malfunctioning nearly bad enough to cause these CAT failures, which is a good thing I guess. Here are some pictures:

https://lh3.ggpht.com/_9izxhPWhYmc/St...0/DSCN1059.JPG

The question still is, is it possible for the catalytic converter to become "depleted" in 190,000 miles of driving on the VX, having not been destroyed by clogging, melting, or fracturing in its past? I've read in a few different places that unaffected by extreme engine problems, catalytic converters should last the life of the vehicle. Is this wrong? I want to be relatively sure that a new Cat will drop the HC @25mph levels enough to pass, before I blow $300 on a new one.

The only thing that I've done that has changed the emissions results slightly is replacing the ECU (this dropped the HC levels by about 20 points). I really have no idea why this happened. The reason I was replacing the ECU was because the EGR solenoid was not grounded by the ECU, and was supposedly not working properly. Fixing that didn't help the NOx levels at all though, but dropped the HC levels.

I'm still perplexed about why the HC levels would be so hugely different between gears but at similar RPMs also. It seems like some engine combustion process is changing between those two speeds, somehow.

https://en.wikipedia.org/wiki/Catalyt...rter#Poisoning

It could have been a simple matter of the fuel trims getting reset.