91 Buick Century

1991 BUICK CENTURY
85,000 MILES • 4 CYL • FWD • AUTOMATIC
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MINIJEWEL2
  • MEMBER
  • 2 POSTS
91 Buick Century starts and runs but has a rough idle and sometimes dies when stopped and chugs when starting off from stop. Changed the throttle positioning sensor, crankshaft sensor, intake manifold, and did a tune up. After changing the crankshaft sensor (the last thing I did) it ran great for a few days and then went right back to the way it was before. I have TWO of the same car and they are both doing the same thing. Please help!
Jan 6, 2011 at 9:14 AM
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JDL
  • ✓Experienced Mechanic
  • 16,098 POSTS
Any applicable mil codes? You should be able to check codes, yourself. Usually with idle issues, I take the throttle-body off and clean it, check iac. Use a gage and check fuel pressure. Any electrical sensor, if there is a problem on the wiring circuit, replacing the sensor won't fix it
Jan 6, 2011 at 9:23 AM
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MINIJEWEL2
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Already cleaned the throttle body and the idle air is fine. There are no codes. They run great when cold but if driven for a while that's when the problems start. If it does die, it won't start again until it sits for a while. I'm sooo confused!
Jan 6, 2011 at 10:10 AM
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JDL
  • ✓Experienced Mechanic
  • 16,098 POSTS
Intermittent issues can be a pain. Test when it refuses to start. Use a known good spark plug or spark tester, carry it in your glove box won't be hot. If plug wires are hot, use a glove, pull spark plug wire off plug. Use tester in boot, ground metal part of tester to metal part of engine, engine cranking, watch for spark.

Vacuum line at pressure regulator, any gas in the line? You have to be careful with gas on a hot engine.
Jan 6, 2011 at 10:27 AM
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