Theproblem

Have a 1995 civic with a zc block z6 head and a d15b7 manifold. 2 catalytic converters, brand new spark wires, plugs, and PCv valve. Cap and rotor are fairly new and the car runs mint. No idle issues at a solid 750. The exhaust is 2.5 inches with 2 catalytic converters no resonator. Before I went ahead and changed everything. The car passed everything with flying colours except hydro Carbons at idle. The limit is 200 I did 475. So I changed the spark wires and plugs and added some methonal hydrate to the gas tank and went back the new reading for hc being 275. so i then I changed the cat thinking it was bad went back and hc at idle were worse at 375. So I got fed up welded the old cat on along side the new one. Put some love in the gas tank ripped the car for half hour and bam 332. I don't know what else to do inspected everything and all looks well but yet I can't pass emissions with a d series someone help!! Reading posed blow
At 2500rpm
Hc(ppm) limit 200 reading 82
Co limit 1 reading 0.53

At idle
Hc(ppm) limit 200 reading 332 fail
Co limit 1 reading 0.47

Ohmega

iTrader: (1)

Why do you have two catalytic converters? I'm not sure, but I don't think it works that way. Maybe someone more knowledgeable can clarify.

It helps to use an OBD scan tool to get some basic engine data, LTFT STFT, O2 voltages. This will help you learn how your engine is running.

TomCat39

This is a 95 so OBD1, no scan tool available.

I also don't believe OP has a CEL so no CEL codes present.

I'm not very versed on emissions as I haven't wrapped my mind on what all the specs mean to the car and it's operation. Some of these guys know exactly what causes what etc.

It's interesting that adding a second cat did reduce things. You didn't provide the details of how your testing is done. I'll get more into that in a moment.

First though, you can revitalize the converters so they work closer to the way they did new. You have to do a hot citric acid bath of the catalytic converter. You can get pure citric acid powder for cheap just google and you should find some sources pretty easily. Then go to the grocery store and goto the baking section and grab one of those aluminum disposable roasting pans that is big enough to hold your catalytic converter. If I remember my research correctly, mix up about a 1:1 citric acid to water ratio. Put the cat in the roasting pan and fill with solution until the cat is fully submerged. You then heat the solution (on a bbq?) to a temp of 150° F (80° C) and let it soak at that temp for 4-8 hours. After words, you rinse it thoroughly with plain water and then you can reinstall. This will bring your cat back to near new condition and operation.

Now, onto the testing. When I've had to do emissions, I first make sure to go for at least a 20 minute drive before I get to the testing place. Basically make sure the cat is fully heated. I then keep my idle high as I wait in line. Simply, I make sure to keep the cat hot up until they make me stop (remove me from the car for the test, wave me to stop etc). Usually I don't get waved to stop until I'm pulled in and they are going to do the test. This way the cat doesn't have much time to cool and it works more efficiently when they dyno run it.

Hopefully some of this information proves helpful.

Theproblem

Thanks for the tips about the cats, but as far as the testing goes I did a lot of research and have done all the things specified ie. Driving the car hard for a while and then going straight for the test even making sure I go right in the morning so I'm first in line and have no time to cool down. And your right it's a 2 speed idle test so no computers involved. Just checked the distributor tho the seal inside is alittle wet with oil could that be causing weird numbers. Just asking because I'm really trying to spend money wisely of stuff that's gonna help me pass. Also could the fuel pressure regulator have anything to do with it. And remember I just failed hc on idle
All other numbers no problem with even hc at 2500rpm

Ohmega

iTrader: (1)

Thank you for correcting me TomCat39.

Theproblem

NotARaCist

iTrader: (1)

Failed HC at idle is your only problem, then? Check your ignition timing. When was your last full tune up, including plugs, wires, cap, and rotor, all NGK?

delsolintegra

I don't have to worry about emissions in Florida but maybe a new engine coolant temp sensor will give exact readings to your ECU so you'll have more precise fuel/air ratios and timing at idle.

Maybe clean the IACV valve also, clean air filter, injector cleaner.

NotARaCist

iTrader: (1)

Different problems have very specific causes. High HC at idle primarily points to ignition. Not any of those four things.

Theproblem

All things said have been check and or changed

delsolintegra

MAP sensor O ring new?

Try different heat range spark plugs just to get thru test.

TomCat39

Okay so if all your tune up hardware is new, play with your ignition timing a little, try retarding the timing by 2 degrees, if that makes it worse then increase timing by 2 degree from proper timing. You should be able to get the results you need with a little tweak.

That's what NARC was eluding to, high HC at idle while all other aspects are a pass, is an ignition issue of some sort. The one aspect of the ignition you can "tweak" is ignition timing.

canadaek

High co would be more of an ignition problem as it is caused by incomplete combustion . Hc is unburned fuel so the air/fuel ratio is off ( to rich) i would look at the oxygen sensor

NotARaCist

iTrader: (1)

Another question, exactly what fuel are you using?

Theproblem

I'm using 91
But for the test added methonal hydrate about 2 leters or half gallon to a half tank of 91.

Theproblem

If the o2 was bad wouldn't it throw a code

eghatch9295

iTrader: (1)

use the gas your car is meant for. retard the ignition timing right before the test to the point that is is just drivable. will reduce your hc.

Theproblem

Let me add as well that this is a car that I purchased recently so all previous work unknown. A couple days after I bought the car I seen that the ignition timing was fully advanced. So I positioned it back to center. Which contributed to lowering my emissions but not enough. I know it's rich cause it back fires like crazy when down shifting and shifts like a b series with no cat but yet I had a cat the whole time and now 2. I guess my question is could of having the dizzy fully advanced for to long have affected the motor and if so what?

spAdam

iTrader: (1)

Did you set it with a light or just eyeball it? The ecu maintains a target idle by varying timing. If you don't have the base timing set correctly it has a tough time learning and you end up pissing in the wind.

NotARaCist

iTrader: (1)

Stop that. Use 87. That alone may solve your problem.

spAdam

iTrader: (1)

Missed that part. Start with the right gas.

eghatch9295

iTrader: (1)

Former User

Prove it.

CEL codes?

existanzcivicb20

What he said I would try to adjust the distributor to advance/retard you timing. Good luck

24TEN

iTrader: (2)

I concur with this statement. It was explained to me much the same way from my friend who has been a smog tech for well over a decade now. I've also experienced the same condition of HC exceeding the max limit for California (to be fair I believe it was at 15mph only) and after exhausting all other options I bit the bullet and had my injectors professional rebuilt. The car passes cleanly now and I even loan the injectors out to my friends that need them for smog use.

Again my smog friend recommended the same advice for my car once before. The idea is that the higher octane is harder to ignite. As "NotARaCist" stated that alone might be the cause of the higher HC (unburned fuel).

EDIT:

My old thread if you feel like reading...

https://honda-tech.com/honda-crx-ef-...rbons-3079979/