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Intermittent Loss of Power or Engine Shutdown - 3.8 L engine

The vehicle is a 2000 Gran Prix with a non-supercharged 3800 V-6 engine.

Over the past year and a half I have experienced an intermittent engine stumble (like the engine had lost power from one or more cylinders) at speeds up to 45 mph and many times the engine would completely shutdown. Once the engine shut down at 75 mph.

This problem had the following characteristics:

1) If the engine just momentarily stumbled, the tachometer would go to zero and stay there even though the engine would continue to run. About three seconds after the engine stumble occurs the Trac Off light would illuminate and stay illuminated until the engine was shutdown and restarted. Pressing the Trac Off switch had no effect. 2) If the engine completely shutdown it could be restarted immediately. 3) No OBD codes were set and the Check Engine Soon light never illuminated.

A Pontiac TSB for a chaffing wire bundle problem was implemented with no chaffing found. The Powertrain Control Module (PCM) was replaced with no effect on the problem. The Ignition Control Module (ICM) was replaced with no effect on the problem. Replacing the Crankshaft Position Sensor cured the problem and it has remained corrected for the past two months.

Even though the Crankshaft Position Sensor is continuously monitored by OBD, it never detected a problem or set a fault code.

Ray

Reply to
Ray Hardy
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Once the engine stalls, the computer can no longer detect a crank sensor issue. This is one of the most difficult issues for a computer to detect.

Reply to
hyundaitech

OBD should catch the failure/out-of-tolerance condition before the engine stalls. The condition is present for at least several seconds and that should be ample time for the OBD to detect the problem and set a code.

On most of the occassions the engine never shut down. It momentarily stumbled then began to run correctly. However the tachometer stayed at zero and the Trac Off light stayed illuminated until the engine was switched off and restarted.

Reply to
Ray Hardy

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