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Testing was done in Maryland on a treadmill with a tailpipe sniffer. The car is a '92 245, LH 3.1, M47 trans, ipd sport exhaust.
Here are the numbers from my first failure back in December:
HC 1.3756, cutoff 1.0, failed
CO 9.4254, cutoff 20.0, passed
NOX 2.0894, cutoff 2.20, passed
In response to this I:
1. Found and tore out a failed pre-heat valve and related plumbing, and capped the hot air hole in the air box. How the AMM survived I don't know, I heard a rumor that LH 3.1 has a tougher model.
2. Tested and replaced a weak coil.
3. Replaced the muffler which had a hole in the tailpipe joint, because I would have been turned away from the second test, clean fumes or not.
I'll have to say the car ran noticeably better and gas mileage went up by almost 3 mpg. I thought I had things wrapped up (ego) but got this surprise a few days ago:
HC 1.5807, failed by a higher margin
CO 8.9388, passed, managed to lower that one
NOX 3.2768, failed where I passed before
I'll admit to a bad move on my part, waiting from December to April to do my repairs. I think those first repairs were good ones, but only part of the job. The only non-test evidence I have that something's not right is occaisional and not very loud detonation at the tailpipe when I upshift.
My theory is that I should test and/or replace the O2 sensor and probably get myself a new cat. The O2 sensor is at least 50,000 miles old, likely more than that, and will throw off the mixture if it's not working well. The little "pops" at upshift are what? high HC, unburned fuel in the escape tubes, enough to perforate one muffler and probably fry the converter. If I don't do something I'll probably lose the second muffler too.
Maryland will wave me through the process after I've spent $450 on emission repairs, but I would get much more satisfaction out of "getting it right."
Your feedback?
Thanks.
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Jim - '92 Red 245 'The Radio Flyer' Recently struck by a tree limb. With replacement body panels, it's not so much Red as Three Tone. Hello Maaco.
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