1991 Oldsmobile Cutlass Cutlass with 3.1 idles very rough

Tiny
MARKBR57
  • MEMBER
  • 1991 OLDSMOBILE CUTLASS
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 161,000 MILES
91 cutlass with 3.1 runs very rough at idle with missing and erratic rpm (maybe 700 - 1200), smooths out at higher rpm when driving, although I can still feel a miss. Idles fast sometimes at start (up to 2000 rpm), but generally does not miss on a cold engine for 5-6 minutes. I pulled trouble codes (got 22, 23, 35, and 53 in that order). Car has new TPS and new IAC valve. I still need to change the PCV valve. I checked all plugs and they seem to be ok. Removed EGR valve and it was pretty well choked with carbon. Cleaned it and replaced it. All the codes keep returning after being erased and engine restarted.

Code 53 is system over voltage according to what I found out. Checked voltage at battery with engine running and got 14.3 volts. The alldata flow chart says the problem is the alternator? Can too much voltage make the engine run rough like this? What do you all recommend?
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Tuesday, July 28th, 2009 AT 11:22 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
I doubt that the alt is causing this unless it's not charging enough. At 14.3, it's doing it's job. Have you checked closely for vacuum leaks? Also, have you checked for an intake leak. The 3.1L are known for having intake problems.
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Tuesday, July 28th, 2009 AT 11:43 PM
Tiny
MARKBR57
  • MEMBER
I have tried to look for vacuum leaks by listening for one. Don't hear any plus tried spraying carb cleaner along where vacuum connections are to see engine speed changed. Would I do the same for intake leaks or is there a better way?
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Wednesday, July 29th, 2009 AT 5:38 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
That would work.
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Wednesday, July 29th, 2009 AT 11:53 AM
Tiny
MARKBR57
  • MEMBER
I replaced the gaskets on the air intake plenum, replaced the pcv valve and hose, checked and replaced whatever cracked or old vacuum lines I could find, and the vacuum level has improved somewhat, but the car still tries to idle fast (1200 up to 2000 rpm). If it tries to reach a lower idle, it usually dies. Rechecked trouble codes and am still getting the 22 sometimes with the 53, sometimes without. Further investigation into the 22 code and the TPS itself shows that on the three wires leading to the TPS connector, I get the 5v reference voltage on one wire, one appears to be a good ground, but the third wire that the TPS signal travels on appears to be dead. I got no response on the multimeter when opening or closing the throttle. I even reinstalled my old tps and redid the test, but got the same result. I'm starting to wonder about my ECM. What do you think?

I have tried to look for vacuum leaks by listening for one. Don't hear any plus tried spraying carb cleaner along where vacuum connections are to see engine speed changed. Would I do the same for intake leaks or is there a better way?[/Quote:4a36b2f356]
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Friday, July 31st, 2009 AT 10:30 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Do it the same way. Be careful. Remember the carb cleaner is flamable.
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Saturday, August 1st, 2009 AT 2:18 PM

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