jeepermat

Forgot to add Ive unplugged the MAF to try and start it in speed density when its acting up, but still no start.

I have a 2008 Yukon Denali with the 6.2 and 150k miles that I am at wits end with. It started about a year ago while driving in the mountains of CO, trucking along at 70mph I let off the throttle to coast and it died, pulled off the side of the road and tried a few times to restart, after 10 minutes it finally started. Ran fine and never did it again until this year. This summer its been nothing but problematic, any time you drive it in traffic when hot it tries to die when coming to a stop at idle, you have to pop it into Neutral and keep the engine above 1000rpm, or it will die. Never sets a code when it does this, it will usually restart after sitting for 10-45 minutes. Always runs fine above 1000rpm. Ive checked fuel pressure when this happens and it was at 55psi, it looks like many others suspect vapor lock with their 6.2's stalling, however I am not convinced that is the case, I can bleed the rail down to 0, and try to restart and it usually wont. I had HPtuners hooked up to it after it stalled and wouldnt restart, I noticed when I finally got it going the voltage was hovering around 12.9-13.1 volts, I thought the alternator was possibly the culprit so I replaced it and the negative cable. It still stalls at idle though, and now Ive noticed when it does it the voltage is still hovering around 13V which seems low even at higher RPM's. Im very suspect that the voltage has something to do with this, however Im not sure whats going on there, the alternator is new and Ive gone through every ground I can find. So far Ive replaced the following -Throttle Body -Fuel Pump -Alternator and battery ground Looking for any other suggestions before I burn this thing to the ground