1998 Pontiac Grand Am Engine keep stalling in real hot weat

1998 PONTIAC GRAND AM
120,000 MILES • 6 CYL • FWD • AUTOMATIC
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CYBERCHIP
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Problem begins after the car has warmed up completely. Engine runs fairly well at high speed, stalls in stop and start traffic or when having to slow down but not stop. Engine usually restarts after it stalls, but, after stalling numerous times, does not readily restart. Sometimes will cut-out while running, or significantly lose power. This happens only when outside temperatures are over 85-90 degrees. This does not always happen in hot weather, and has never happened in cooler temperatures. This has been a problem since the car was new, but recently the problem has gotten much worse. Because it happened so infrequently in the past, no one has ever been able to diagnose the problem.
Apr 27, 2009 at 2:06 PM
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JACOBANDNICKOLAS
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Has the check engine light ever come on? Has anyone ever tested fuel pump pressure?
Apr 27, 2009 at 8:56 PM
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CYBERCHIP
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No, the check engine light has never come on. The fuel pump pressure has been check, and appears to be normal.

Thank you so much for your help!
Chip
Apr 27, 2009 at 9:55 PM
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JACOBANDNICKOLAS
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Make sure there are no vacuum leaks and the catylatic converter isn't plugging.
Apr 27, 2009 at 11:11 PM
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CYBERCHIP
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A check of the vacuum system did not show any deficiency with vacuum. The exhaust system does not show any severe back pressure indicating plugging of the catalytic converter. I realize this problem makes no sense. The car runs great then outside temperature is below 85-90 degrees. It is only in very hot weather that there is a problem.

Thank you,
Chip
Apr 28, 2009 at 2:24 PM
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JACOBANDNICKOLAS
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When it gets above that temp, check fuel pump pressure. The pump may be failing.
Apr 28, 2009 at 8:12 PM
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CYBERCHIP
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I was able to get that fuel pump pressure reading. It is between 43-45 PSI. I also checked for DTC codes with my new scanner and everything with the scan passed. No trouble codes were reported.

Thank you,
Chip
May 1, 2009 at 11:32 PM
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JACOBANDNICKOLAS
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It sounds like an ignition module.
May 2, 2009 at 1:11 PM
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