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danb.jn832
danb.jn832 2/1/2013
1991 Buick LeSabre Custom 6Cyl3.8L - Engine
engine turns over fine but wont start, stutters bad & sometimes backfires. should'nt it give a check engine light?
has a new batt. & Alt. no present codes but did have a history code 34 which points to MAF sensor. I took it off and car ran great so engine is fine. Replaced MAF sensor, car didnt want to start at first, but once i got it started it ran great at idle & road test. After sitting for about an hour im back to square one car doesnt want to start and it backfired damaging the air filter. no codes present. OBD1 system. im thinking TPS, or IAC but shouldnt I get a code for these sensor?
2 Answers
  • HouseCallAuto
    HouseCallAuto 2/1/2013
    In '91, the computer tracking for faulty sensors was not accurate at all. Most likely cause of your no start would be a bad ignition control module (easy to replace but expensive part) or a bad crankshaft position sensor (inexpensive part but requires removing the harmonic balancer to replace).
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    HouseCallAuto
    danb.jn832 2/1/2013
    ignition module is good all 3 coils are firing. will engine run good with bad Crank PS? with MAF off and in open/loop engine run good for about 5 - 10 min. my experiance with CKP sensors is car wont start at all, just turn over.
  • HouseCallAuto
    HouseCallAuto 2/1/2013
    The IAC will not cause any running issue besides stalling out or an incorrect idle speed. The TPS could go bad and usually sets a code 21 or 22. You can manually check the TPS with a digital ohmeter but if it is in question, just replace the sensor as it is not big money and is easy to replace. You said you replaced the MAF sensor so that rules that out *unless* there is a code 34 resetting even after replacing the MAF. Your symptoms do sound like MAF sensor but you said it is new so I went past that. You did say if I understand correctly that at this time "engine turns over fine but wont start". So explain what you mean in further detail before I comment further.
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    HouseCallAuto
    danb.jn832 2/2/2013
    thank you for answering. Right now I can get it to start barely but it sputters real bad and if I don't play with the gas peddle it will die out on its own. there is no codes, it backfired once bad messing up the air filter, never happened before. i'm thinking fuel problem sence no codes?
    HouseCallAuto
    HouseCallAuto 2/2/2013
    No, you cannot make that jump for a '91 as the computer is just not powerful to detect and set codes like OBDII systems are starting in '96. This being a 3.8 '91 GM car, the classic things that cause hard starting and backfires are coilpack and crank sensor. The coil will not set a code and the crank sensor does not always set a code when they are intermittent.
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