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.

Thanks.

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

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.

Problem is only after shutdown while warm/hot.

Do you disagree?

Edited April 13, 201610 yr 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.