dboatrig

My 1990 3.0 v6 2wd pickup failed AZ smog check today (CO failed). The truck has 109K miles. I'm the original owner. It has never failed smog before. Here are the test results:

HC grams/mile: passed @ 1.34 (2.00 allowed)
CO grams/mile: FAILED @ 65.34 (20.00 allowed)
NOX grams/mile: passed @ 0.04 (4.00 allowed)

I jumpered the diagnostic terminals, and no codes are being reported.

I have had the transmission removed, and exhaust pipe removed (from block to cat) for almost a year, in my first drawn-out attempt to replace clutch/pilot bearing/throwout bearing, and rear main seal. Truck has been garaged in Phoenx area entire time. I finally got it all back together this weekend. After recharging dead battery, truck started and ran fine after a few seconds of cranking. Truck now starts right up, and drives just fine, no different than ever. I did re-connect the O2 sensor. Gas in tank was same as a year ago, but I filled it up 2 days ago with fresh gas (was near empty, so near full tank of new gas). Truck was driven a few miles with new gas before test, if that matters.

So, I'm thinking maybe bad O2 sensor, or dirty injectors. Am I on the right track? I thought a bad sensor would throw a code, though. Did letting it sit so long cause this maybe? Or is it more likely a coincidence? O2 sensor has never been replaced. Any thoughts? Thanks.

kodiak90

Is your O2 sensor before or after the catalytic convertor? The sensor might be corroded or have some build up on it. Try taking it out and cleaning it.

keithdphan

bad catalytic converter or the cat. didn't reach operating temps to remove CO's. what i do is run the truck on the freeway right before dropping the truck off to get smogged. this makes sure the cat. is plenty hot to do its job. gl!

dboatrig

Thanks for the suggestions. Dealer said cat works fine, sensor is fine. Replaced distributor, wires, and plugs. Truck passed emissions with these results:
HC: 0.24
CO: 6.81
NOX: 0.65

I am convinced that the smog guy did not release the parking brake. They are not used to the t-handle setup. I don't know how else the numbers could be so vastly different. I don't believe plugs, wires, and distributor cap would have such an effect, especially since the trucks has run fine the whole time.

Thanks.