We have a 2003 6cyl GCL with 78,000 miles and about a week ago it started with a little bucking while driving, like for an instant it felt like it was not getting gas and also stalled a couple times when coming to a stop. No check engine light and tried to start it it started instantly.

Had mechanic look at it and fuel pump, cam shaft position sensor, throttle position sensor, crank shaft position sensor all checked out OK.

He suggested it might just be some bad gas, ran fine last couple days.

Friday on a trip on an interstate, 40 miles from home, when again experienced a slight "buck" when on a slight incline doing 65. A mile later still driving at 65, felt another buck, started losing speed and realized it had stalled. Coasted to the side. Not out of gas, had a full tank. Plenty of battery power. Would not start. Turned key and all the service lights/air bag lights etc came on, but none of the gauges moved, would not start. Sat and tried for 45 min before AAA showed up and towed us back home to our mechanic. Again, checked all the above and everything checked out. After that put the key in, turned and it started back up perfectly - a total time elapse of 4 hours from when it conked out. We had our mechanic checked the PCM screws and they were short so it wasn't grounding out. We have spent hours on different forums seeking out an answer and it is frustrating!

WE don't know what to do. Suggestions? Many thanks! Kathy

 

Sounds like possibly something electronic. Electronics can fail when heated, I'm thinking possibly something in the ignition system causing weak or no spark.

It could also be vapor lock, the fuel rail or injector getting too hot, causing loss of fuel. When the motor cools the issue goes away.

I would try and check for good spark and fuel immediately when/if this ever happens again. A motor needs 3 things to run. Air, fuel, spark. Figure out which is failing, go from there.