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1995 Pontiac Firebird Stalling, Idle issues and highway &q

Tiny
SGT_WRIGHT
  • MEMBER
  • 1995 PONTIAC FIREBIRD
  • V8
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
My Trans Am recently had the ignition control module, distributor, EGR, PCV vavle and ignition coil replaced. After much frustration due to the high repar cost (all of this work as NOT required to cure the initial issue), I noticed that the engine would "cough" on the highway under load. As I noticed the engine temp going up to normal operating range I pulled over to have a peak under the hood. As I slowed down the engine stalled. It started back up, but only after many seconds of turning over. The idle was kind of low so I adjusted it slightly, and now it is right back to where it was.

Please help this tired and frustrated ole American soldier :)
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Tuesday, March 17th, 2009 AT 5:18 PM

9 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
From one ol' soldier to another, do you, or have you had, a check engine light while driving? If you have, I'll need the code #s and descriptions.
It sounds like a "lean" condition. How old is the fuel filter? Please advise. You may have to do a fuel pressure test on it.
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Tuesday, March 17th, 2009 AT 6:20 PM
Tiny
SGT_WRIGHT
  • MEMBER
  • 5 POSTS
No codes are showing, and the engine is running pretty rich at the moment (you can smell it and you can see the black soot on the tailpipe). Fuel filter has been replaced AGAIN (just incase) and the fuel pump has been replaced (but not to sure as to how propperly it was installed. Gotta love "know it all" buddies). I was wondering about the IAC or the brake booster. But im just a "low level" tech, so I wouldnt trust my instinct :)
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Tuesday, March 17th, 2009 AT 6:58 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Sarge, Opions are like but holes, everbody has one. A question on your first post, and I quote, As I noticed the engine temp going up to normal range", Did you mean "above" normal range? If yes, what was the problem when you opened the hood?
Also, from what you've posted, It sounds like it may be a problem with the idle speed control, ISC, unit. These are usually just carboned up and be removed and cleaned with an ordinary can of regular carb cleaner. The ISCis located in the intake manifold by the throttle body. Check this out and let me know.
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Tuesday, March 17th, 2009 AT 7:49 PM
Tiny
SGT_WRIGHT
  • MEMBER
  • 5 POSTS
Well after taking the IAC out I noticed it wouldnt move AT ALL, even after cleaning. I replaced it and everything seemed to work fine. I did however notice that the inside of the intake manifold was faintly coated in fuel. Not sure how that came about but that could have explained some of the backfires I had.

After everything was working I only had one small "tiff" with the vehicle. It seems like there is a bit of a delay between hitting the gas pedal and the car actually responding. Sound like a TPS issue?

BTW you have been a GREAT help so far A+++
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Friday, March 20th, 2009 AT 5:59 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Raw fuel in the intake manifold is indicative of an injector bleeding down when you shut motor off. This will sometimes require you to crank the engine over for a bit before it fires. It takes a few seconds to build fuel pressure up again.
The ac problem shouldn't be related. It may just be low on freon.
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Friday, March 20th, 2009 AT 7:50 PM
Tiny
SGT_WRIGHT
  • MEMBER
  • 5 POSTS
Leaving the base today it began it's hesitation again. It only hesitates when under load, and when the engine is in normal operating temperature (IE going uphill after the vehicle has ran for 5 minutes +).

Now that the fuel pump/filter, distributor, coil, control mod, plugs, wires, PCV, EGR, IAC, and an old vaccum line have all been replaced im out of ideas other than the fuel pressure regulator.
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Saturday, March 21st, 2009 AT 9:08 PM
Tiny
JAMES W.
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Sarge, when you're going up hill, under a load, does it buck and spit or is it like stepping in a pile of mashed potatoes-nothing happens? This will help narrow it down.
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Saturday, March 21st, 2009 AT 9:36 PM
Tiny
SGT_WRIGHT
  • MEMBER
  • 5 POSTS
It doesnt "surge" like i've heard some people say. But it really DOES feel like "steppin in mashed potatos."
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Sunday, March 22nd, 2009 AT 8:29 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
Try unpluging the mass air sensor and running it up and down the street a couple of times. In doing this, it will set a code, but that's ok. See what difference it makes in driveability.
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Sunday, March 22nd, 2009 AT 11:19 PM

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