2000 Jimmy...towing...hot weather...loss of power

Hi folks, I have a 2000 Jimmy, 4.3L, which runs normally at idle and when not towing a boat.

Problem occurs when it is hot out (85 degrees +), when I am pulling a trailer (my boat) and on a long trip (usually a 3hr+ drive). At the end of the long drive the truck does not accelerate when the gas is stepped on, I coast to a stop. If I step on the gas the engine dies. It will start and idle but will not provide enough power to move. Engine does not run rough - in fact it runs great on the hiway until the end of the drive,, after about 3 hrs the problem occurs.

This happened today and I let it idle in the driveway for 30 min. Unhooked the boat and all was OK as I drove around town.

I have had it in to 3 mechanics who can't figure it out. There are no codes thrown at all. Any ideas where to start? Fuel filter was just replaced.

DId u figure this out yet? If u did, interested in hearing...

Couple things
- in my opinion, sounds like fuel supply (pressure regulator or pump)
- however, this could be timing. Need to check all the lines crossing your exhaust manifolds on both sides. You may have electrical TOO close, heat increases resistence which buggers up input to your computer. Use some plastic ties and and pull ALL your wires up and away from the heat.

I am no mechanic however, when I bought my jimmy I had a 10 year gmc mechanic look it over because I was having issues loosing power on long trips. I would loose power after two hours or so and when I went to hit the gas I had no power. we took out the oem Thermostat and replaced it with one that made it run about 20 degrees cooler and I gained about 5 hp and never had the problem again. I now have over 280,000 miles on the original engine thanks to a $3.00 part.

hope this helps.

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