99SuburbanTX

I have an intermittent issue for your review. I can only seem to recreate this behavior when the truck has been sitting for about 24 hours without being driven and when it is cooler outside. Since I live in south central Texas, that means before 10am. Suffice to say it is hard to have time to diagnose.

The truck starts fine, idles fine. It does fine under partial throttle getting out of the driveway. When you go to accelerate away from home it all of the sudden falls flat on its face. Total loss of power. You need to peg the throttle to keep it from stalling. Once you get up to 10~15 mph the issue goes away. You can even get good acceleration from 20 to 60 without hesitation. Depending on how severe it is wanting to be, this may be the end of the problem for the rest of the day, or it may continue on for the next 4 or 5 stoplights. Then the issue goes completely away until you let the vehicle sit for another 24 hours.
When this happens, the check engine light does not come on. No codes can be found. The only codes I have had recently were for Bank 2 running lean. At the time I removed the bank 2 sensors and cleaned them. Codes went away. I do have new O2 sensors to install. However, these codes have not been seen for 2+ months.

I checked the fuel pressure to look for fuel pressure regulator or injector issues. It hold pressure just fine. It seemed a little on the low side per my Haynes manual (54psi vs 60~66psi spec in the book), so I have replaced that. This was not a complete waste as my fuel gauge is now working again.

Any thoughts on what could be causing this condition?

in2pro

Throttle position sensor?
might check the connection to the sensor maybe when its cold it not making god connection but is okay after it warms up from the engine heat...