High carbon monoxide

[AZmike]

Last week my hatchback failed its first emissions test. Everything was ok except for loaded CO; it was measured at 3% with a 1.2% requirement. Idle CO was fine.

I've read that high CO is typically caused by a rich mixture so I tested:
O2 sensors (about a a year old, both passed service manual test)
intake temperature sensor (passed)
water temperature sensor (passed)
I don't have a fuel pressure gauge, so I could not test the pressure regulator.

I also replaced the spark plugs and reset the timing. The old plugs looked a bit worn, but incomplete combustion would be hydrocabons anyway, but I figured it wouldn't hurt. The car runs well and usually gets >35 mi/gal so I doubt it's running rich most of the time.

Does high CO during the loaded test only point to a particular component? I was stuck in line at the test a while so my catalytic converter might have cooled off enough to have lost some of its effectiveness.

Any suggestions before I try the next test? Has anyone had good luck with the 'guaranteed to pass' fuel additives under these conditions? This is the last year I need the car to pass. I was planning to go at a less busy time and hope that with the converter hot I could get by.

I'd appreciate any suggestions.

[Dr_Snooz]

I just wrote this the other day in response to another high CO thread. See if it helps.

http://www.3geez.com/forum/showpost.php?p=1077838&postcount=3

[ecogabriel]

Please read the article in the link below; it gives a list of potential causes for different types of emission failures

http://www.auto-repair-help.com/auto_diagnostics/diagnose_emission_test_failure.php

I found another, courtesy of toyota

http://www.autoshop101.com/forms/h56.pdf

[88LXi68]

you could try using some of that guaranteed to pass or 2 bottle of dry gas. I have had varying luck with both.

[AZmike]

I went in Monday night with a hot exhaust and zero wait. I got the numbers the car typically has for the past few years: clean loaded test and acceptable idle numbers. The lesson learned is that I should only go when the wait time is short. I appreciate the feedback.

[Dr_Snooz]

Congrats!