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Old 10-14-2009, 05:18 PM   #31
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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.
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Old 10-14-2009, 06:56 PM   #32
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Assuming that my catalytic converter is actually depleted, which is supposed to never happen.
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.

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Do you guys think there is any possibility of the EGR being (in theory) non-functional causing the CAT to become clogged up?
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.

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Maybe I should take my cat off and take a look inside.
Wouldn't hurt.
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Old 10-15-2009, 06:49 AM   #33
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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).
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Old 10-15-2009, 09:12 AM   #34
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Maybe 1 or 2 EGR runners [...] are plugged with carbon
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?
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Old 10-15-2009, 01:25 PM   #35
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Not sure- here's a thread http://www.gassavers.org/showthread.php?t=8721
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Old 10-15-2009, 01:33 PM   #36
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Yeah, ok... looks like a sub-manifold / distribution rail setup to me.
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Old 10-15-2009, 03:15 PM   #37
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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: http://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.
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Old 10-15-2009, 03:27 PM   #38
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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.
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Old 10-15-2009, 08:33 PM   #39
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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:



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.
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Old 10-15-2009, 09:21 PM   #40
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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?
http://en.wikipedia.org/wiki/Catalyt...rter#Poisoning

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