One our trucks at work is a 2006 Mega cab with a quad xzt box it. The guy driving the truck pulled off the edge of the road the other day and noticed the truck was missing at idle. It missed for a few seconds, then all of a sudden revved all the way to 3500 and held for about 3 seconds, dropped to idle, then did it again. When it fell back to idle the second time, he turned the truck off. Waited a few minutes, cranked it back, all is well.

I checked all the connections on the quad harness, and they all were tight. For now we have pulled the xzt and the harness off to try to eliminate the problem. We will see how it acts over christmas.

Any ideas or things i can check for? There is no check engine light on, but i haven't hooked up my smarty to check for codes that way....

 

do you have a means of checking rail pressure? is this the truck in your sig that has the recon?
put it back on, leave the display in the R/p mode, and when it is acting up, check the r/p
at idle it should be between 5-7K psi, cruising somewhere around 16-19K, WOT 23K and up to 25K.
once you get a reading, repost with the pressure and where the throttle was at the time of malfunction.

 

No, its not the truck in my signature. The truck we are talking about does not have a rail pressure gauge. The strange thing is, the throttle position should be at 0% when the truck was acting up.....it was idleing rough, then revved on its own to 3500 twice.

 

Check your TPS!
Better yet just replace it!
Cheaper than an engine!