03 Suburban Bad idle and stall when hot.

[likestrucks]

I need some insight. I have an 03 Suburban. L59, 140k. After driving in hot weather, if I idle it will be normal, then the revs will drop low and it will want to stall, then it revs up over 1000 and then settles back down to normal. It does this over and over and sometimes stalls. While it's wanting to stall the gas peddle doesn't effect the chugging. 

It did this last summer in the heat. I changed fuel filter, O2 sensors, and MAF sensor. I have checked the fuel regulator to see if it is getting fuel on the vacuum line side but it's dry. I have cleaned the throttle body. I haven't tested fuel pressure but I don't think it's the pump because it ran normal all fall winter and spring.   But now that the hot weather is back it is doing it again.  

No codes. No missfires being logged. Long term fuel trim will jump up over 25 on bank 1 and 2 while it's wanting to stall. Then when it settles back down the trim goes back down to around 8. Temperature sensors all show proper temperatures for everything.  Does anyone have any ideas?

[CamGTP]

I would be curious to see what the fuel pressure is doing though. It might be falling and that is why the fuel trims max out because of the pressure drop in the rail. The injectors are no longer spraying enough fuel with low pressure.

[davester]

Yeah, I would second check fuel pressure with a guage, both at idle and when you speed up the engine to say 3k rpm.  The pressure can drop a bit while it's speeding up, but should return to full pressure when the rpm levels off at the higher speed.

[C1A]

Sounds like 2 different issues going on... Bad idle could be air filter or injectors need cleaning. Or even a fuel cap. Also  check radiator cap for running hot.

I have a 2010 LT. It runs like new with 230k.