2000 Pontiac Grand Am Throttle body response issue

Tiny
BZ2LRW
  • MEMBER
  • 2000 PONTIAC GRAND AM
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 244,000 MILES
My problem has become very dangerous at times, if I depress the throttle body quickly the engine will hesitate (like the old chevy quadrojet carbs I used to have on my hot rods), depress the gas pedal too quickly and the car will stall. Depressing the gas pedal sllooooowwwwly. There is no hesitation or stall. Obviously this is very dangerous if you are entering traffic from a stop, or turning left at a stop light in front of oncoming traffic for the fact that if you forget to "ease" into the throttle. The engine will stall. And you are panicking to restart. Replaced the TPS and helped my idle a little. Please help. Frustrated in Michigan
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Wednesday, August 4th, 2010 AT 1:10 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Do you have the 3.1L V6?
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Wednesday, August 4th, 2010 AT 6:36 PM
Tiny
BZ2LRW
  • MEMBER
I have the 3.4 motor forgot to mention that. Sorry
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Thursday, August 5th, 2010 AT 7:50 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Has the check engine light come on? Also, have you checked for both vacuum leaks and the fuel pump pressure?
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Thursday, August 5th, 2010 AT 11:57 PM
Tiny
BZ2LRW
  • MEMBER
First I will apologize for not giving as much information as I could have from the beginning. I consider myself to be a very educated diagnostic tech from past experiences and employment history, unfortunately, I have none of the scan equipment that I had at my disposal while working for GM Milford Proving Grounds as a prototype vehicle tech. I have had the vehicle scanned at auto parts facility and the codes that were set were issues with the camshaft positioning sensor and crankshaft positioning sensor. If I remember it correctly, I was told the codes said they were "out of sync". In my opinion, my best guess was that a vehicle with 244000 miles could quite possibly have a timing chain with enough wear to cause this symptom. But I might be wrong for thinking this. I took a back yard mechanics approach at resolving the issue by replacing the mass air flow sensor, but it did nothing for the issue. I will include this information as a help to you (if I haven't bored to the point of not reading further) I replaced the fuel pump at 175000 because of failure and the vehicle has good pressure (tested vehicle with fuel pressure gauge installed on fuel rail tap while driving). I replaced the tps last month because of failure (3000 rpm idle). I have checked for vacuum leaks. None found, I have inspected all components visually but have not dug into the voltage testing on each individual emissions components as I should do. I was hoping to research forums with a quick resolve for this problem from someone who has experienced the same issue. Final comment, I could go to dealership with my check book in hopes of better scanning equipment to diagnose, continue with the pathetic replace this part and see what happens concept, or continue from the comfort of my couch on my laptop, eating a bag of chips and watching COPS on my TV in the background! Thank you so much for taking the time to respond.
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Friday, August 6th, 2010 AT 10:39 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
If they are out of sync, you are most likely correct with the timing chain. The only other thing I can think of is if one has come loose.

Don't you miss the old quadrojets?
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Saturday, August 7th, 2010 AT 1:04 AM

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