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Debbie Harris's 1969 Grand Prix

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'97 Grand Am 2.4

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My wife's Grand Am sometimes stutters and/or stalls when accelerating from a stop; usually happens after being shut down hot for ~20 minutes to ~2 hrs.  Throttle position sensor checks OK except output voltage at wide open throttle = 4.27V; manual says should be >4.5.  Closed throttle = .44V (OK), Reference signal to TPS = 5.04V (OK) and ground checks good.  Voltage increase/decrease as throttle is opened/closed is smooth; no change if TPS is lightly tapped while opening/closing.  All checks done after engine warm.  No codes, no engine light.

Any knowledgeable input will be appreciated.


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have you checked vacuum? I don't get why it only does it when its hot, are you hearing any new noises?

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Thanks, Ghandi.  Have not checked vacuum because it didn't seem pertinent, given the symptoms:  

A) It runs perfectly and starts almost immediately nearly every time.  Also true when restarting if it stalls as described.

B) Problem is only after shutdown while warm/hot.

Do you disagree?

Edited by Mars
No new noises. Has been doing this for years and literally 10s of thousands of miles. Have not been able to track down.
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