Engine Performance problem
1999 GMC Yukon V8 Two Wheel Drive Automatic 100000 miles
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1999 GMC Yukon 5.7 2wd auto. The truck starts and runs fine for about the 30 minutes, then starts to stall / bog when trying to accelerate. The more it is driven and the more heat generated (hot days, running AC) the worse it gets. Eventually it will not be able to accelerate above an idle.

I feel that this is heat related because the longer it's driven, the less usable throttle you have. You can pull over and sit for 5 minutes and get about 5% throttle back.

I have put a code reader on it, and there are none. The service engine light never comes on. Fuel pump and filter are less than 6 months old.

I guess I'll keep adding to my question until some body knows the answer.

So far I have replaced the TPS, Cam position module, Distributor Cap and Rotor, Knock Sensor, Checked fuel pressure (no less than 50 psi).

I put a timing light on it and noticed that as you start to increase rpm, the timing advances, then when it starts to bog, it throws a large amount of retard.

If I could find out how giving it more thottle retards the ignition, I think I could end this madness.

Don't be shy, come on in, the waters fine.