Failed emissions test on CO (at tailpipe). Readings about the same at idle and 2,500rpm. CO 5.68%. HC fine at 280ppm. Car runs perfectly, no starting or drivability problems, used as a daily driver, 45,000kms. New hyper cat and O2 sensor. Synthetic oil, new plugs, etc. I am surprised with the high reading, as I would expect some drivability problems. Had the test run a second time, similar readings. Mechanic did make co mixture screw adjustment, did take it down a bit, he didn't wan't to lean it out too much, so problem not solved yet. Before I get into more sleuthing with the mechanic today, I would like some ideas of what would cause the ok HC but high CO readings. Other threads help, but appear to deal with idle and drivability symptoms, which I don't have. Ideas? (thanks)
I replaced my cat and actually got a 0 CO reading. Are you sure your cat is working? Exhaust should be noticeably hotter after it passes through. Muffler shops have temp gauges and can eliminate this as a potential source of your problem in about 5 minutes.
Even if you test before the cats, you should see .7% plus or minus .5%. This is the "generic" Bosch spec. A properly running engine should produce this with test pipes and NO cats. You don't have anything really wrong except for the gross adjustment. Have your guy bring it down more and as long as the HC doesn't climb, you're set. Make sure you "reve" it in between adjustments but NEVER "rev" it with the 3mm allen tool in it. Seal the hole when you measure. Always adjust from lean to rich, never the other way. I would only be worried if I saw the HC substantially above 300 ppm. Good luck. -Peter (ah, good old K and KE Jetronic) www.peterkrause.net
Extremely helpful comments, reinforce what I supect, but I want to give the mechanic some benefit of the doubt, these things tend to be simple or complicated, not much in between. Will report back what I learn. The timely repsponse is much appreciated.
Changed dist cap and rotors, wires, probably needed anyway (had the parts lying around for sometime, whew, that rear bank is no fun to change out the cap on). Had retest, still a problem, couldn't adjust CO without HC skyrocketing. Mechanic giving up, as cars runs perfectly. In order to get a conditional pass in Ontario, if one spends $450 on repairs,etc., you are good for a pass, although you can't resell the car. So I said fine to solve the probelm for a couple of years while I figure out more creatively what the probelm might be. He suggested a fuel injection flush and intake cleaning, to at least get some value for money. When he ran the flush, crud and black smoke came out quite dramaticly. After driving the car to clear residual gunk, the car was retested, and passed, right on spec!! Must have been clogged injectors, rather surprising since there were no drivability problems. Seems almost too good to be true...but I guess we all get a bit of luck now and again...
