I just had my car smoged and it failed the 2500rpm test.
The only problem was with the CO %.



I've seen a lot of posts about the NOx being too high, but not so much with the CO. I believe high CO indicates incomplete combustion due to rich conditions.
What are some possible reasons this could be happening?

Also, a little background. The same thing happened last year. It failed the same way and I did a tune up (plugs, wires, cap rotor, oil&filter,K&N air filter, fuel filter). I had it tested again at a different place and that time it actually did a little worse than before. Same problem though.
Defeated, I had them run a diagnostic. As part of their diagnostic they ran a pre-smog test and it looked like it would pass so they ran the full smog and it passed with flying colors. Weird.
Thanks

 

I probably should have mentioned I have a 92 Firebird w/ 3.1 V6

 

Hey there Blaze, I had the same thing happen to me. I didn't want to mess around with CA tough smog laws, so I took it to a shop. My problem was a bad EGR valve. Did a re-test and it passed with no problem.

Shortly after this, I joined TGO and read up on this problem. See Technical Articles on main page, General Repair: The Lowdown on Code 32 (EGR) .

Also, search for threads about EGR/Code 32 and you'll learn even more. My problem was described in this information and on how to check for a bad EGR valve. Had I been aware of this site sooner, I could have saved myself some money. But, that's 20/20 hindsight. Good luck.

 

Thanks for the reply.
I'll have to check out the EGR valve.

In the mean time, I discovered something and I am wondering if it could have an effect on smog.

I noticed my engine temp was constant (highway, city, w/ AC, w/heater, etc...). And I think that temp is lower than I remember it being.

I think the temperature reads 160ºF, the needle is halfway between 100º and 220º. (I'm unsure because the scale on the gauge is wacky. 100º to 260º with 220º being in the middle. WTF?)

I thought the thermostat might be stuck open. I think I remember reading that the emissions equipment need the engine to be at a certain temperature.

I put in a new thermostat and my normal operating temperature went up to about 190ºF.

Could this have had an impact on the smog results?

 

Hey Blaze, what type of t-stat did you put in? I know that the V6 should run hotter than V8. I believe a stock replacement V6 runs open at 195º. This would put you on par with your current temp reading. The one you replaced may have been at 180º or 160º. You may even see an increase of your fuel milage with the new t-stat. So Blaze, let me know what temp you installed OK. I don't want to make guesses in helping you.

To answer your question, It may have a slight difference. If your previous t-stat was set at 160º, and the car engine may be too cold. Whereas, factory specs say it should be hotter, and this you may have already confirmed. I'll keep checking on your post.

 

I just checked, the stock thermostat is supposed to be 195º, and this is what I put in.
It will be a week or so before I can re-smog it again. I have to wait for the AC Delco O2 sensor I just ordered. I've read the Bosch can make you car run rich, which is what my car is doing.

Could I have a problem with the EGR even if the check engine light isn't on?

 

Just wondering, do you have the special deep socket for removing the O2 sensor?

From what I've read, the EGR valve isn't part of the electrical circuit. This shouldn't be bad if there's no light on or no Code 32.

One way to check that it works. It has a spring in it, but it isn't that hard to press it up. You should be able to do it with just one finger/thumb. Once you press it up, put your finger over the nipple where the vacuum line connects to it. Now stop pressing up, and see if it drops back down. It shouldn't. If it comes right back down, or even drops back down slowly, it's a bad EGR, and needs to be replaced. Some members have recommended to use a can of carb and choke cleaner to clean the EGR valve. This may free it right up, and you may not need to buy another one.

Also, check the EGR solenoid - it may be disconnected, it may have bad wires at the connector or in the harness, or the solenoid could be bad. Check your vacuum lines and make sure they are not cracked, or broke in any way.

I'm a little surprised that you're not getting more help on this issue. There's a lot of knowledgeable people here on TGO and I'm only relating what I've learned from this site. I hope it helps.

 

Ok, I’ve done some work and I think it’s almost time to smog it again. I just want to ask a few questions.
First here is what I’ve done:
Distributor rebuild:
Module
Ignition Coil
Pickup Coil
Cap
Rotor
Two of the metal fingers were bent away from the pole piece. I bent them back so they all line up with the pole piece.

Spark Plugs
Oxygen Sensor
Oil & Oil Filter
Fuel Filter

All the parts I replaced are AC Delco.

I’m running rich at high rpm, is there anything else I didn’t change that could cause that.

In my searches I’ve noticed the EGR valve gives people a lot of problems. Could there be a problem with the EGR that wouldn’t throw any codes?

The only other possibilities I can think are the fuel pump and the fuel injectors.

What do guys think?
Should I smog it again or continue investigating?

 

Smogged it this morning and it passed.

 

Finally, good news. Now you get to drive it in the clean California air .