failed emissions

My 1991 GP w/122k miles on it failed our emissions test twice! The first time it was high on Hydrocarbons failed (1.42 with a .8 standard). The Carbon Monoxide passed (13.0 with a 15.0 standard). NOx wasn't graded, but it read 2.08 with a 2.5 standard, and CO2 was 397.6 and passed.

I figured that it just needed to be warmed up a little better and drove it for an hour home from work and had it tested again. This time Hydrocarbons failed (1.04 with a .8 standard). The Carbon Monoxide passed (10.0 with a 15.0 standard). NOx read 2.3 with a 2.5 standard, and CO2 was 405.0 and passed.

I've got a clean air filter and fresh oil. The car runs great on the highway, but after reading a few posts, I'm thinking that it may need a new catalatic converter. The warming that I did and the improvements I saw with Hydrocarbons may prove it. Is there anything else I can do that would save me a little cash and get me pass the inspection? Someone mentioned an adjustment to the fuel pressure to lean things out a little. Where do I make that adjustment?

Basically you answered your own question. Go for the CAT convertor. If you're looking to save money buy a universal style CAT instead of an OEM. In our area they run about $95.00 including installation/labor.

Good luck!

When I checked through the maintainance records, it shows that the CAT converter is only two years old. I'm going to try some Sea Foam in the tank for now. Any other ideas?

You might also try an emissions fuel additive that can be found at most auto parts store's.

Larry,

Glad to see that you are still with us! I thought you dropped off the face of the earth since I haven't seen any posts from you in a while. Your expertise is always valuable in the Pontiac forum.

Lynn

After the fourth try, the car passed with a .70. There was a .80 standard. Luckily, in NW Indiana there's no charge for the test itself. The only change I'd made from the 1.42 hydrocarbon test to the passing test was a couple hundred miles with some 93 octane gas and a can of the Sea Foam in the last half tank. Thanks for your suggestions!