1989 Chevy Celebrity Rough Start/Idle/Running

1989 CHEVROLET CELEBRITY
363,727 MILES • 6 CYL • FWD • AUTOMATIC
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JOHNNYJR
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My car initially starts OK; but the Service Engine Soon Light comes ON in about a minute When I park it then start it again within an hour, it runs really rough, surges and the exhaust smells (the Light comes ON again, too). When I am travelling along, the light goes out (city or highway driving); but when I slow down (either taking my foot off the gas or applying the brake, the trouble light comes back ON again accompanied by rough running.
When I tried to retrieve the trouble codes, I got some weird readings: 12 OR 21, 13 OR 31 and what appeared to be 5-4-3 (flashes of the light).
I suspect I may have a bad Oxygen sensor.
May 4, 2009 at 9:05 PM
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JOHNNYJR
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I found the vacuum line on the back of the MAP
sensor had fallen OFF. I couldn't see this because of how the unit is mounted on the 2.8L MPI engine. I had knocked it OFF when I changed out the alternator. Once I re-installed the vacuum line/tube, my "Service Engine Soon" MIL no longer came on - NO new fault codes, either!
This simple fix solved my problem.

NOW .. I just have a Death Wobble (front end) to solve; and my car will be highway-worthy.
May 18, 2009 at 7:12 PM