my vx just failed smog
 

I have a federal civic vx, the one with lean burn. It has 240k on the original engine and transmission. Engine compression is good, tuned up recently. Ignition timing is correct. Engine runs good and does not burn oil. The car already has an replacement catalytic converter installed. I took it apart to fix an exhaust leak and the cat looks good, its not clogged or anything.

I live in San Francisco and we have the enhanced smog. I failed the 25mph test , but it passed the 15mph test easily. I forget to get the print out, but the only thing that it failed on was hc. Mine read around 250, which is gross polluter status. The CO and NOX was was very low. The smog tech thinks it might be a lean miss fire.

So my question is does lean burn kick in at that low of a speed? Usually if the car pass the low speed, it can easily pass the high speed. Is there anything that i can do to turn off the lean burn feature for the smog test. To see if indeed it is a lean missfire caused by the lean burn. We tried to adjust the timing but it did not effect the hc reading. Has anyone else fail on just the high speed hc, but pass everything else?

Sorry to hear about your emissions problems. I remember when emissions testing first came to my area. The Buick failed miserably. I had to buy a new carbureator at $1,200 to fix it and make it pass. I'm glad its exempt now. I'm sure it needs a new carb again, but I think this time I'm just going to put a normal carb on it and ditch this expensive computer controlled crap that doesn't work. Rusty's latest emissions test proves that an old vehicle with a carb can still pass emissions with pleanty of margin to spare.

-Jay

Just smogged my 94 intrepid with no new items at all in the last 4 years or so. It passed with no problem. Original converter,pipes. What i did was drive it for about 30 to 45 minutes before the test. You might have thought of having it smogged out of the Frisco area. They are nuts in that city. You did a lot to your ride and it should have passed with no problem. Maybe put in hotter plugs use higher octane, just some thoughts. The Intrepid has 167k on it and is seldom driven.

keep it in 1st gear, there is no lean burn in 1st gear according to my dmm in my vx.

Yes, that is always good to do that... The last time I had to get the Buick to pass emissions I did that. I took her out on the interstate and ran her at 80 mph for 20 miles. I then pulled off the highway, and into an inspection station. I left it running in the parking lot until they could get it in. The inspector was suprised and told me he lost a bet because it passed.

-Jay

Hmm, I just recently smogged my VX here in the bay area with the Federal ECU and it passed no problem. The car had 200k miles with only the basic tuneup stuff done. What causes high HC??? I would look that up online to see what fix is recommended...

Hycrocarbons (HC)*
A list of common causes of HC related smog check failure:

1. Ignition Timing Advanced above specifications.Timing is measured in degrees. before or after Top dead center. If your vehicle is required to be at 10b degrees and instead is set at 16b degrees your HC emissions will increase. ( b = before top dead center ) .

2. Ignition system problems. Parts like the ignition coil, distributor cap, distributor rotor, ignition wires, spark plugs.

3. Vacuum leaks, Gasket leaks that cause vacuum leaks. Broken, disconnected or misrouted vacuum hoses.Vacuum component failure such as a power brake booster.This causes a very large vacuum leak.

4. Catalytic converter failure.

5. Air injection system problems. ( Smog pump and related components )

6. Engine damage (burned valve, low or no compression in one or more cylinders).

7. Sensor problems and or computer problems can cause a Smog Check failure.

You could go on and on for a few more pages, but these are the main causes.

I am not sure if i can run the test in first gear because the smog machine wants the test to be done in a certain rmp range, so you will have to change gears.

The timing is correct, we tried to retard the timing but it did not help.

Tune up parts are good, but will recheck and check the fuel pressure.

swap in a cali ecu and you will pass with flying colors
federal ecu will not pass

I dont want to buy an ecu just to pass smog. I have not looked at the wiring diagrams yet, but if i can disable the "lean burn" than my federal ecu would be like a CA ecu. Or if i can turn my 5 wire o2 sensor into a 4 wire sensor. If the check engine light comes on, it does not matter. The catalytic converter was properly warmed up, plus we tried four different times on the smog machine.

I double checked the tune up parts, and decided to change the distributor cap, rotor and ignition coil. The coil looks like its going to crack. It probably wont affect the smog, but it needs to be done.

Lean burn on this engine doesn't cause a lean misfire. And a lean misfire doesn't cause high HC, it would instead cause high CO.

No you can't run it in 1st gear because it has to be at 2000 RPM.

They already heat it up as part of the test so the old "run it on the freeway in low gear" doesn't apply.

I passed just fine with a federal ECU in San Diego. Passed with over 220k miles and w/out doing any maintenance upon buying the car (was planning my now completed engine swap).

Lean burn will give you high NOx, not high HC's. HC's are partially burned fuel. You're not running rich cuz your CO is low. So most likely your problem has to do with the ignition.

I know you said your ignition timing was done but was it done to VX specs? I know most Hondas are 16 degrees base timing but the VX may be 12 I'm not sure. If it is in fact correct then try the high side of spec. You can go 2 degrees advanced. This may raise NOx though.

Run 87 octane. Change your spark plugs and ignition rotor. The VX uses different spark plugs than what the auto parts stores are going to want to give you (DX plugs), so research it yourself first. Get NGK or Denso brand only.

If you wanted to force it into 16 valve mode (not recommended) you could apply 12v to the VTEC solenoid. This will help your NOx but not your HC's. In fact it will most likely increase your HC's.

Yep, try an ignition tune-up... I also smogged a Federal ECU based VX with 200k miles and no issues. There is something else wrong for you not to pass.

David

I believe the smog tech knows emissions and is correct - lean misfire.

High HC in a lean misfire makes perfect sense because either the air fuel mixture is too lean to burn or the A/F mixture is not getting an adequate spark, hence the fuel does not ignite and it exits the car as unburnt fuel.

It is interesting that it only shows up in the 25 mph test. Difficult to understand how such a small difference in rpm/speed could be the tipping point.

Air - Fuel - Spark. Troubleshoot until you find which is the root cause of the misfire. It could be the distributor, spark plug wires, fuel pressure regulator, alternator, vacuum leak, the list goes on and on. Good luck and I hope you pinpoint the cause quickly. I would be very sad indeed if I couldn't use my VX because of emissions. Just love that 50 mpg.

Based on my experience with my VXs I would suggest:

Looking at the top dead center/ crank shaft position/ cylinder position sensors. All of which reside in the distributor and can give bad information to the ECU if they are not working properly. In turn the ECU will respond with bad information back to the engine. I replaced my distributor with a NEW not rebuilt distributor because rebuilts are often very poor quallity. The new distributor actually costs about the same as a rebuilt anyway.

Checking the Map Sensor next. Honda's Trouble Shooting Guide lists the MAP sensor as a possible problem when the vehicle fails the emissions test. It can reveal itself as a lean misfire if the information to the ECU doesn't express the engine load correctly. This is even a more acceptable choice since you are not experiencing a problem from one load level to the next. I always replace mine initially.

The LAF sensor is also on the list but since your car passed the low speed I feel it is probably working correctly.

The EGR and its controls (D15Z1 only) are also listed and are a likely possibility since their operation is during the timeline you describe.

Fuel pressure and injectors can cause such problems but usually reveal themselves as a loss of power and/or rough running under cruise conditions. How does your VX run under acceleration?

Under evaporative emissions control you might look at the evap purge control solenoid on the back of the intake manifold for a vacuum leak at the speeds where you experience the problem. (Unlikely)

Yes, my VXs go into lean burn in first gear and as I recall 10 mph is the low VSS requirement.

Don't mess with the LAF sensor. The parameters that are engineered into both the LAF sensor and the ECU depend upon each other. There is a preset voltage range supplied to a 5 wire: 2 sensor wires, a sensor ground, and a regulated resistor for the heater input. Since five wire LAF sensors have two zirconium elements as opposed to the four wire's one, it's not possible to run your ECU with a four wire.

Good luck!

Thanks for all the info guys. I rebuilt my distributor today at work. I changed the cap, rotor, coil, distributor seal and o-ring. Oh by the way the spark plugs were replace less than 5k ago and i tested the them and they are good. I dont want to replace anything that is not bad, because i want to see if i can pin point the root of the problem. I also checked the fuel pressure and its within spec. I will set the timing tomorrow. And by the way we tried messing with the timing during the test and it did not effect and emissions readings.

Another thing that i just remembered was that when i first bought the car the car just passed smog. But then again i bought it from a guy that ran a smog station. So i cant be sure that i actually passed the smog test. But the car had two cats on it. It had a factory replacement catalytic converter and a converter welded under the car. I originally thought the front cat was plugged, but when i took it apart to fix an exhaust leak. It look fine and looks to have been recently replaced. So i removed the second cat under the car. It was killing the power a little.

After i check a few things, i will try to smog my car with it in 16v mode. I assume that once its in 16v mode, it will not engage lean burn.

Maybe that's why he had 2 cats under the car, because he couldn't get it to pass otherwise...

-Jay

I know why it was there. I was just trying to see if i could pass with one cat. The 15mph is suppose to be a harder to pass than the 25mph.

I went to the smog station retested my car after the repairs that i listed above. The results were the same. I passed the 15mph and failed the 25mph, HC in the 300 range. While the car was in the 25mph test, i manually put the car in 16V. And the HC dropped to 70, which is in the pass range. The CO and NOx went up, but still within the pass range. But I now fail the 15mph test. HC(75), CO(.6) and failed the NOx 1000.

When i put the car in the 16V mode, the cel came on. The limp mode is cutting off the egr and causing the engine to run a little rich.

My next smog test will be with the vtec solenoid energized along with the oil pressure switch on the solenoid bypassed. Then the car will be in the 16v without the cel. I will also clean the egr passage. I dont want to smog it again.

rx7will,

How does your car drive? Mine has the exact same problem (federal car, failed smog due to high HC @ 25mph, co and nox very low).

I ask because I think this may be related to the smog, but my car doesn't have smooth/consistent power delivery. When it's cold it runs fine, but when it warms up it randomly bogs/misses/hesitates/stumbles on acceleration and also under constant load and rpm. It will alternate between this and running fine.

I put in new spark plugs and wires and it still does this. I just bought a new (5 wire) O2 sensor, so I'm gonna try replacing that this weekend. I'll let you know if that makes a difference.

It feels like it's constantly kicking in and out of lean burn. Sudden loss of power, then surges, then loses power again. Does your car do this too?

what's your spark plug gap? how much is it to retest? this probably won't make much of a difference but maybe you could try gapping them closer if your coil is weak.

I gapped the plugs to the factory spec and i have a brand new factory coil.
Mad Pup- I can stay in lean burn if i am easy and steady with the gas pedal. I does not just fall in and out of lean burn by it self. My car accelerates smoothly, it does not miss and surge. My car use to run like your car, i replaced the O2 sensor and it fixed the problem. But my car had a code for the O2 sensor so that made it simple.

How about disconnecting the LAF sensor? I know for sure that my VX will run fine with it disconnected and I presume that it will not go into lean burn...

Disconnecting the LAF will cause the cel to come and and put the car in limp mode. Thats what happen to my last smog test.

I just passed smog on the vx, i was running out of time with the registration. I made another attempt to keep the ecu from going into lean burn. I failed again, so i just had another cat welded onto the car. I used a Honda Ridgeline cat. I installed a new cat on the Ridgeline because the car ran over a log and it dented the cat. The insurance company wanted it replaced. I kept the old one, the outside was dented but the core was not broken.

If i had more time i think i would have tried a different approach.

I dont notice any difference with two cats on the car.

This scenario would give you high CO. The difference is CO is unburned fuel, HC is partially burned fuel.

I wouldn't blame lean-burn or 12 valve mode being that Honda sold how many VX's and yet they all pass smog? It clearly is not a design problem but a maintenance problem.

Get a valve adjustment. If that doesn't solve it then either your compression is low or you have an ignition problem. If you rebuilt your distributor you still have the same cam/crank sensors. Try another distributor. The Z6 shares the same distributor as the Z1. Perhaps you can find one in a junkyard.

Just an update- I was experiencing similar symptoms as rx7will (see my post, #18). After replacing plugs, wires, 02 sensor, and cat, I found that my timing was severely retarded (5 deg. BTDC!!!). Set it to the stock 16 deg BTDC, and voila! The low power, hesisation went away and it passed smog without any problems.

I'm loving my VX now. It feels so powerful! Hahaha!

hmmm wow. bad laf here too or i soldered a wire wrong(cheap buttconnected one from egay). hopefully my replacement 1 will do it. additionally i'm going to 2 kitties. An old VX/cx oem cat up by the head & a new cat welded after the B-pipe connection. glad some are passing . mine is federal ecu and jdm d15b Vtec-E. I'll be changing the jdm IM also cuz it looks like a dx/ex IM with a bigger TB for sure. I bet the more air =more fuel even with that 49state ecu. post results after i retest in a few days.

Why? For more power?

Increasing the air ie load will increase the amount of fuel the car burns but it wont alter the air fuel ratio unless you reach a point in the calibration where it's tuned for a richer mixture.