What could cause hesitation at about 1500 RPMs

Tiny
PRIORFAM
  • MEMBER
  • 2000 PONTIAC GRAND AM
  • 125,000 MILES
When car initially gave me trouble it was jumping at about 1500 rpms after it warmed up then progressively got worse and was doing this when cold also.I had unplugged map and tps sensors to see how it would react. Eventually brought it in to have it diagnosed and they said tps sensor code was indicated and would cause the symptoms. They replaced the tps sensor and said it was all set after test driving. However I picked it up and its doing the same thing after warming up. They said now theyre not sure but leaning towards pcm? I don't trust theyre evaluation. Its hesitating at 1500 to 2000 rpms and can't drive through it, its idling fine. Thank you
Saturday, October 29th, 2011 AT 5:27 PM

4 Replies

Tiny
BRYBAKER
  • MEMBER
  • 1 POST
Are there any other symptoms? I have never had a problem with the TPS or the map sensors. Is it throwing any other code? I had a problem with my 2001 Grand Am when the intake manifold gasket broke and began to leak. I had no knowledge that this had happened until my engine started working extremely hard to gain speed (3500 RPMs to get to 25mph). If you have lost coolant recently this may indicate a leak in the manifold gasket. When this leaks, coolant is burned in the exhaust and clogs your catalytic converter causing back-pressure into the engine, especially when the exhaust system is HOT. If you are car savvy check around your manifold and see if you can spot any leaks or signs of problems.

Good luck!
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Monday, October 31st, 2011 AT 1:40 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,052 POSTS
The TPS code may have been on since you disconnected it. Have you checked fuel pressure? Have you checked to make sure there are no vacuum leaks?
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Tuesday, November 1st, 2011 AT 4:32 PM
Tiny
PRIORFAM
  • MEMBER
  • 2 POSTS
No other codes but there is some leaking around the intake manifold so I think ill start by replacing intake gasket and go from there. Thank you for your advice.
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Tuesday, November 1st, 2011 AT 10:30 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,052 POSTS
Check if the leak is coolant.
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Tuesday, November 1st, 2011 AT 10:55 PM

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