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1994 Pontiac Firebird enginge surge

Tiny
RALPH KESTER
  • MEMBER
  • 1994 PONTIAC FIREBIRD
  • V8
  • 2WD
  • AUTOMATIC
  • 28,000 MILES
5.7 liter runs fine when the engine is cold. After 15 to 20 minutes of stop &go driving when stopped at a light the engine will suddenly "stumble" for a few seconds the tach up an extra thousand rpm for a few seconds. Doesn't happen when cruising down the road, just when stopped. The problem is more severe when car is in reverse backing into garage. Check enginge light does NOT come on. Have replaced plugs, wires, and intake manifold gaskets on recommendations of various mechanics. Nothing has helped.

Any suggestions?

Thanks,
Ralph
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Friday, July 23rd, 2010 AT 2:18 PM

1 Reply

Tiny
F4I_GUY
  • MECHANIC
  • 3,302 POSTS
Sounds to me like you have a vacuum leak or a faulty idle air control valve.

My first test would be to measure fuel trims via a scantool. If they are above +10 on short term or long term, then you most likely have a vacuum leak.

Get a propane torch, open up the tank (don't light it) and with the vehicle on, move it around all the gaskets and hoses. If you don't find the leak this way, have a shop smoke test the engine, this will find the leak.
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Friday, July 23rd, 2010 AT 4:06 PM

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