92 Honda Civic VX Failed Smog High HC at 25pmh

[mars]

My 92 Civic VX D15Z1 49 state(with EGR) failed smog @ 25 due to high HC. Here are the results:
15mph RPM 2474 CO2 14.3, O2 0.1, HC max 96 meas 28, CO max 0.59 meas 0.03, NO max 859 meas 689 Pass

25mph RPM 2319 CO2 8.7, O2 7.7, HC max 79 meas 146, CO max 0.51 meas 0.02, NO max 798 meas 382 FAIL

Replaced sparkplugs, O2 sensor with new OEM Dealer, ECU P07(eBay- used) Retested

15mph RPM 2452 CO2 14.4 O2 0.0, HC max 96 meas 37, CO max 0.59 meas 0.04, NO max 859 meas 434 PASS

25mph RPM 2209 CO2 9.0, O2 7.3, HC max 79 meas 123, CO max 0.51 meas 0.02, NO max 798 meas 516 FAIL

For both above tests, Timing is 14 BTDC according to smog Tech

I removed the brand new installed spark plugs after about 200 miles and #4 (close to the distributor) looks white and nice, #3 & 2 partially black, and #1 completely black.
Any help is appreciated.

[jrodz09]

BUMP!

I am going through the same exact issues. My VX cannot seem to pass smog.l and my tags are do by the end of the month with smog certification so any information or suggestions would be greatly appreciated.

Same as OP my car has a "lean misfire" according to the smog technician. It runs everything else fine except for the O2% @ the 25mph. Believe it is at 7.x% which in turn is causing my HC to shoot at 96 measured with a 76 or so maximum. Been trying it all:

-K&n air filter cleaned and recharged
-oil change
-ngk spark plugs
-distributor rotor only(rest of distributor looked carbon less)
-pcv valves cleaned. (1 by intake manifold and 1 by breather box)
-cleaned out egr and ports. Intake manifold. Iacv. Breather box. Throttle body. Injectors operated fine on the test. How fine. Don't know.
-seafoam through gas tank. (Out of the system now)
-new gaskets. Intake manifold. Throttle body. Egr.
-ignition timing was off. Mechanic adjusted with timing gun.

Other than that car seems fine. No jerking. Smooth in and out of lean burn. Gas is lasting now. Was averaging about 300 miles on a tank. Sad. Now it's looking better. Driving it to San francisco for New Years so that be a test. Just don't know why it's a lean misfire and not passing smog. Uncle suggested a cat converter replacement. I got the federal and the cat converter seems difficult to find.

[mars]

Unfortunately I was not able to get my VX to pass the smog. However, after buying new O2 sensor (LAF) from dealer ($500+++), swapping engine with one with 90k miles, replacing ECU (bought one from eBay), spark plugs, fuel filter, etc, etc, etc, I took the car to the dealer, in Sacramento for specific diagnostic on lean condition @25mph with O2 7.5%. I payed $120 for diagnostic waiting next day to find out what was wrong. Next day they called me and said that after 2-3 hours of testing, they couldn't figure out why the O2 is so high. I was told that they need more time for diag, etc, etc. Also they said that the CAT is bad, but is not available from Honda. I called the referee program for part not being available, and they sent me a part exemption letter. I was lucky to find two previous passing smogs certificates for my car, and with these in hand I went back to the dealer and I showed them that in the past the car had same lean condition and it passed smog. They called the Honda factory and said that there were no specs for the VX model and therefore they give me a new statement (free of charge) stating that this lean condition is normal for the VX platform, bad CAT, not available. I set up a referee appt and with the part exemption letter from BAR and with the diag/statement from dealer I was able to get my sticker for 2015. Praise God!! However, the referee warned me that in two years I will have to go through the same process. He was not really convinced about this "lean burn condition" as being ok.

[jrodz09]

Wow! This is ridiculous. Luckily you got your situation squared away. I am going to go ahead and attempt a few more.. Like order some wires, perhaps a close to OEM distributor. I believe right now I have a BOSCH which is nightmares with the Honda cars. Also try to find an aftermarket cat that can be used. We will see. I will keep this posted since no one else wants to share any information other than us. LOL. Thanks once again.

[user removed]

Originally Posted by mars

My 92 Civic VX D15Z1 49 state(with EGR) failed smog @ 25 due to high HC. Here are the results:
15mph RPM 2474 CO2 14.3, O2 0.1, HC max 96 meas 28, CO max 0.59 meas 0.03, NO max 859 meas 689 Pass

25mph RPM 2319 CO2 8.7, O2 7.7, HC max 79 meas 146, CO max 0.51 meas 0.02, NO max 798 meas 382 FAIL

Replaced sparkplugs, O2 sensor with new OEM Dealer, ECU P07(eBay- used) Retested

15mph RPM 2452 CO2 14.4 O2 0.0, HC max 96 meas 37, CO max 0.59 meas 0.04, NO max 859 meas 434 PASS

25mph RPM 2209 CO2 9.0, O2 7.3, HC max 79 meas 123, CO max 0.51 meas 0.02, NO max 798 meas 516 FAIL

For both above tests, Timing is 14 BTDC according to smog Tech

I removed the brand new installed spark plugs after about 200 miles and #4 (close to the distributor) looks white and nice, #3 & 2 partially black, and #1 completely black.
Any help is appreciated.

Run a couple of cans of Chevron techron through the fuel system and see if the plugs look better. Fixed a low speed miss in my Sentra in 19 miles. Pretty cheap at Wally World.

regards
mech

[comegetme]

It looks like I'm having the same issue. All values are in range, except HC at 25 mph. Question: Will temporarily swapping in a CA ECU from eBay for the smog test likely resolve it? My understanding is that with the CA ECU, the car does not go into "lean burn", and thus behaves exactly like a Cali VX. Seems obvious, but I'm wondering why the previous posters did not go that easy route. Your thought are much appreciated.

[California98Civic]

I kinda understand the lean burn system in the Honda but not completely thoroughly. Still, I'm pretty sure HC is not the primary side effect of lean burn. NO would be the high level from lean burn it seems to me. So I'm not sure changing the ECU, oxygen sensor, and harness to convert the car would be such a good idea since the problem might be elsewhere. Also, when the technician plugs into your OBD port he's gonna be looking for the proper ECU in the car. He'll be identifying it electronically. I'm not certain, but you might fail just for having swapped out the ECU.

A thought that I have is that perhaps the CAT is really old. There is a process for cleaning the catalyst using a combination of citric and oxalic acid. It seems to work from what I have seen people do online with it. And the process was scientifically proven to work in a lab. I did it with my own catalyst but my procedure for the testing of its effectiveness got botched. So I can't personally vouch for whether it works or not. But I have no codes showing. The CAT on my civic is 18 years old. Try cleaning it?

[comegetme]

Thanks, California98Civic!
Can you please give me details on the cat cleaning procedure? What product exactly (Amazon?), and where exactly put it in and how? Thanks!

In the interim, a mechanic discovered that the exhaust pipe was missing the second catalytic converter, and put in a new CA C.A.R.B. approved aftermarket cat into the exhaust pipe below the car for $100 part + $50 labor.

I remember that some threads on this or similar forums suggested that there was no second cat on the VX, while others disagreed. I have two more Civic VX's - one has a second cat and a resonator, the other has a resonator but no second cat. The car in question had no second cat nor resonator underneath. A certified CA smog + repair station was first surprised about my newly installed second cat and refused to work on it due to modifications, then looked up the part for this car and confirmed that is was the right part.
This is all very confusing. The diagram on https://www.hondaautomotiveparts.com...EXHAUST+SYSTEM is not clear to me either. I don't see the second cat listed as a separate part.

IF we assume for the moment that the car originally had, and should have, a second cat, can someone perhaps educate me what is the difference in function between the primary (at the exhaust manifold) and the secondary cats? Do they just work in tandem to eliminate a higher percentage of the gases, or is one responsible for one type of gas and the other for another pollutant? I am having a hard time finding information on this, and most discussions on this forum just mention "the" catalytic converter.

If there is doubt whether all VXs had a second cat, can you VX owners please peek under your car if you guys have a second cat? (As I just learned, the cat is not to be confused with the resonator, which has a more round shape and is typically further to the rear in the exhaust pipe. The resonator and/or catalytic converter may or may not be on the cars after exhaust pipes were replaced.) Thanks in advance!

Regardless of whether or not the car should have a second cat and whether the mechanic putting it in did the right thing, the car also has significant less power accelerating than my other VX's. That means something must be SIGNIFICANTLY off. However, no check engine light. (Check engine light is working, but shows no code.) Several mechanics already found every conceivable part related to exhaust working, except the car has ca. 280 HC at 25 mph, AND significant loss of power. At least one mechanic confirmed that he did a compression test.

The engine bay looks almost sparkling new, car looks immaculate, and the car has only 190k miles.
Federal car, 5-wire O2 sensor. Should pass smog in CA according to the information on this forum, if all parts are working. EGR valve, throttle body, O2 sensor, spark plugs, wires, PCV valve, and rotor are all new with the best NGK/NTK parts where available.

I made an appointment for tomorrow at the dealership for a full diagnosis. I don't know if their diagnosis will be more exhaustive than the one of the smog+repair station. I'm afraid they come back with no result either, and/or refuse due to non-availability of Honda parts (catalytic).

If the dealer's diagnosis is non-conclusive, I guess the next thing to replace is the primary catalytic converter. The HC values stayed almost the same before and after putting in the secondary catalytic (under the car). Question: Is it possible that replacing the primary catalytic with a C.A.R.B. approved aftermarket catalytic will fix the HC, if the secondary didn't move the needle a lot?

What are my other options? Giving up and take the loss? I paid several thousands for the car.

Any help is very appreciated!

[comegetme]

On another note: the car does not only look almost-new, but also gets 55 mpg! However with much less acceleration power compared to other VXs. The high mpg would suggest to me that the combustion cannot be that much off from specifications. But what do I know

P.S.: I get conflicting information from different mechanics whether the high HC means "lean" or "rich" combustion. All smog values are in range, except HC is 280 at 25mph. (That's many times the max allowed value!!) I'm not sure how mechanics who do this stuff day in and out for 30+ years can come to so different and conflicting conclusions ("lean" vs. "rich") of the high CO value?! I showed the exact same copy of the same smog result sheet to the mechanics!!

[comegetme]

I just called Honda customer service to determine if the VX came with one or two catalytic converters. They put me 10 minutes on hold, only to say they are unable to determine it, and referred me to a dealer. Looking at the diagram https://www.hondaautomotiveparts.com...EXHAUST+SYSTEM , I am unable to determine if parts 9 and 11 are interchangeable or different configurations. If i interpret it right, part 9 seems to attach to part 5 which looks like a catalytic converter, while part 11 seems to attach to the exhaust pipe. What do you guys think?