1989 Pontiac Firebird High idle

Tiny
BOOMER1
  • MEMBER
  • 1989 PONTIAC FIREBIRD
  • V8
  • 2WD
  • AUTOMATIC
  • 125,000 MILES
After it warms up, begins to idle high, around 1,000-1,100 rpm. Car seems to run well. But when I shut it down, it will not start. 2 hours later it will start.
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Monday, January 18th, 2010 AT 11:31 AM

4 Replies

Tiny
ERNEST CLARK
  • EXPERT
With a high idle, I'd say you have a vacuum leak. Check all of the hoses under hood and replace any if they are suspect.

As for your car not starting after shut down, will the engine crank over or not? I'll need to know this before I can attempt to narrow that down.
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Wednesday, January 20th, 2010 AT 9:58 AM
Tiny
BOOMER1
  • MEMBER
The car cranks over, no problem there. It seems like it needs to cool down before it will start again. Could it be flooded? IAC motor was recently replaced for another problem, as well as the fuel injectors.
I've checked for vacum leaks and have had no luck. I will check again.
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Saturday, January 23rd, 2010 AT 1:24 AM
Tiny
ERNEST CLARK
  • EXPERT
If there's no black smoke coming out of the tail pipe after it warms up, then it isn't running rich. (A reason why it would be flooded) So I would generally rule out a leaking fuel pressure regulator. Besides, if it was a leaking regulator, it would be harder to start the longer it sits, not the other way around.

I'm not exactly sure, since I haven't worked on an HEI ignition in so long, but you should have an "Vacuum Advance Diaphram" on the side of your distributor.

Sometimes this thing will get corroded and stuck open, which will advance your timing (And raise your idle). And if your timing is advanced when the engine is cut off, it will certainly make it harder to start.

Do you have a hand vacuum pump? If not you can rent one from a parts store.

With your engine running, disconnect and plug up the hose that leads to your vacuum advance canister. Then connect the vacuum pump and apply 10-12 Hg of vacuum. This should raise your idle slightly and you'll hear it. (Usually you want to connect a timing light and measure the advance. But for the sake of keeping it simple, you just want to verify the advance isn't stuck)

If you'd like to check your timing at this moment, you sure can. But you'll also have to rent a timing light. And I'm not exactly sure what your initial timing should be (6-8 degrees BTC), so you'll have to look that up.
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Saturday, January 23rd, 2010 AT 8:15 AM
Tiny
BOOMER1
  • MEMBER
There does not seem to be a vacum advance diaphram on my distributor.
I did check the vacum pressure at several points, and the pressure seems to be good at 19-20 hg.
As the car warms up to operating temperture, the idle goes up to 1,000 - 1,100 rpm. Then it won't start.
Any other ideas?
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Saturday, February 27th, 2010 AT 9:47 PM

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