Hi all,

Well just got back from the inspection center and my car failed for CO emissions. It was so close too!!!

I failed for CO% (carbon monoxide). Results were 0.88 and the standard is 0.65. So damn close!!! My other emissions were great NOx was 440 standard is 879 and my HC was 82 and standard is 117. Anyways I need to figure out how to fix this since I don't have the cash to take her in to the shop.

My car has a 107k on it and I try to take care of it as best I can. Excessive carbon monoxide suggests that my air to fuel ratio isn't correct from what I have read. Guess the question is where do I start.

I really don't use the car in the winter so I don't know if that played into me failing. I ran the car for a good 30 minutes on the highway (to heat up up the cats) and was online at dmv for at least an hour (car was on).

Parts that are new:
- Oil Changed more then 6 months ago (mobil1)
- Catco Catalytic Converters (2006)
- Bosch Oxygen Sensor (2007)
- Plugs & wires (2005)
- Rotor & Distributor Cap (2006)
- PVC valve (2005)
- Fuel Filter (2006)
- Engine Timing was checked in 2006 and it was fine

Any thoughts?

 

There is a product you can get at any auto parts. The advertizing claims it will help you pass emissions test. Don't remember that it's called but several people on here have sworn by it.

 

Thanks for the reply z28SORR,

Ha yes I have seen the product. But heres my thinking...if the car has excessive CO emissions something is up. Granted the engine has 107k on it but ideally with all the maintenance I give this car I am hoping to get some insight on the cause.

All the other numbers were excellent except the CO(carbon monoxide)

 

what was the temp when testing. NOx can go up
get it hot like have them run it (stationary) to opperating temp, then rev to 2500 RPM (stationary) for 2 mins to precondition cat then test right after.

if you warm it up HC unburned gas will go down so will COs , NOx will go up but you have room

how old is the EGR?

 

Hi HottestZ28,

Not sure about the temperature of the car. I know that when I was online the fans kicked on. Whether they both did or it was just 1 I don't really know. The temeperature guage on the inside of my car I think is off. I actually put in a fan control switch with thermostat in a few years ago. I did that after my mechanic told me the guage wasn't 100% accurate especially on the f-bodies.

The car was run on dmv's dyno. I know they ran it for what seemed a long a$$ time compared to other cars in the other lanes.

I have never changed the EGR on the car.

The CO was the only gas out of EPA standards everything else was wonderfully low.

 

what happens is if your car is on the borderline of failing it gives it more time to (clear up) before it issues a fail. If you can get your cats stoaking hot your cat will clean up more gasses. If you fan control switch is set lower then stock thermo temp that will make it run alittle more hc and co's and lower NOx. an open or failty EGR can lower NOx and also make the combustion chamber run cooler not alowing for "complete burn".

 

Interesting HottestZ28 I guess that makes sense and thats why it was on the dyno longer. I turned off my fan switch as soon as I left my house figured that would get the car to stock heat and cooling.

So a faulty EGR could be the culprit. I am actually thinking about picking up an ADSL cable and hooking it to the car and my laptop to see if I can figure it out. Wouldn't a faulty EGR trip a fault code on the ECM?

 

Add timing? Anyone know if that makes exhaust cleaner with more combustion time avaliable? I think RS cars only had 0 degrees of base timing...Maybe bump it to 6 degrees? Goodluck!

 

no i am not saying that your egr is bad at all. just a possability. Tripping a fault code- I wouldn't really see how it could in a 92 nothing to test it other then if it was really bad totally open all the time making a poss map sensor code, but you would def feel that.

 

Hmm guess that makes sense.

 

What was the timing actually set at?

 

I believe its 6 degrees or -6 I would have to confirm that tomorrow. But I double checked the timing last year with a timing gun to factory spec.

 

Another idea, is try a new air filter, they're cheap and might just do the trick.

 

Sure no expert, but this is interesting. Not running overly rich but an incomplete burn. I'd check to be sure you're using an ethanol blend gas, would help this deal I think. And try premium grade as the slower burn might clean it up a bit. I wonder if a couple bottles of gas dryer would help, it's mostly alcohol I think. Might unhook the battery cable for a minute, get back to the untrimmed factory fuel program. You're really close to passing, that's a tough one.

 

Yeah thats the killer so close to passing. Forgot to mention I run 93 octane on the z28. The battery on the car was reconnected a day before I took the car into inspection. From what I have been told on the boards it only takes the car a few miles for the ecm to learn its pattern (fuel/air mixture).

I have 2 k&N air filters in the car with less then 5k on them as well.

Anyone think perhaps the charcoal filter needs to be changed?