Re: Perfect CO, elevated HC - can anybody comment?

Do you have a distributor on it, or is it electronic. If it's a distributor, check the cap. If the points on it are worn or corroded, that may be it. My
dad had the same problem on his Honda, the HC's failed. He gave it a tune-up, replaced the spark plug wires and replaced the distributor cap, and it passed. If it's the electronic ignition, it may be faulty. I'm no expert, but I think if the spark is bad or not a full spark, then it doesn't completely combust. That may be why you're getting high CO, CO2 and even O2 numbers. Hope this helps.
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Thanks for the advice, tweliver. This vehicle has a distributor, but no points - it's electronic ignition, with a Hall sensor pickup and the the infamous TFI module controller. I will scope the ignition - the computer in this car is not smart enough to self-diagnose a misfiring cylinder, though I would expect an elevated CO in such case, uneven idle or driveability problems. My question was whether anybody can point me to something which causes elevated HC, but does not cause an increase in CO.
I am NOT getting HIGH CO - on the contrary - it's practically zero. As for CO2 and O2 - I think that the higher the merrier. High CO2 shows that the exhaust is coming out of the tailpipe, and does not go anywhere else. High O2 (though I am not sure that mine qualifies for high - there is no limit) most likely just indicates that the thermactor (air pump) is doing its job...
IK

distributor,
My
tune-up,
passed.
think
combust.
this
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IK opined in

Yep... the disparity points back to

Warm the car up up, change the oil, then drive it at highway speeds for 30 minutes.. take it back to the test and I bet you find the results are a lot different.
Ever look down the throat of a TBI at cold idle? The gas just dribbles out of the injectors..

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IK opined in

Seems to me, that's been a "Hot Tip" for passing the E Chack for some years... and yep, if the oil gets a fair amount of raw gas repeatedly and is driven for primarily short trips, to boot, it certainly wont help.
Blowby, and valve seal problems can contribute.
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