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1991 Chevy Cavalier idle surges up and down and bouncing oi

Tiny
SEAN_ZACKER
  • MEMBER
  • 1991 CHEVROLET CAVALIER
  • 6 CYL
  • FWD
  • MANUAL
  • 130,000 MILES
I have a 1991 cavalier has a 3.1 v6 5 speed when the car is idling it idles up and down only sometimes and when the idle drops down and then back so does the oil pressure idk changed the tps and iacand no change almost like the engine is surging also has a miss only at idle cant find a vaccum leak anywhere
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Thursday, November 19th, 2009 AT 11:41 PM

5 Replies

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Got to be a vacuum leak somewhere, IAC is attempting to compensate but can't because of leak.
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Sunday, November 22nd, 2009 AT 7:51 AM
Tiny
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  • 3 POSTS
I have checked all over I can here like a pss pss sound but might be the exaust cause its not all the way tight at the flange
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Sunday, November 22nd, 2009 AT 8:36 PM
Tiny
MMPRINCE4000
  • MECHANIC
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You can spray carb cleaner at suspected vacuum leaks, any change in idle is where the leak is.
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Monday, November 23rd, 2009 AT 7:02 AM
Tiny
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Ok I just did that and found nothing I need help
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Tuesday, November 24th, 2009 AT 12:30 AM
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
You need a scanner that can read live data. Watch the movement of the IAC (called "steps").

Most shops can generate smoke that will migrate toward the vacuum leak.

You could try a compression and cooling system pressure test.

But it could also be a leaking injector seal, intake manifold gasket.

Also scan timing advance.
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Tuesday, November 24th, 2009 AT 7:22 AM

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