Engine stalling when decelerating. HELP

GMSEEDENALI · February 19, 2016

2007 GMC Sierra Denali 6.2l AWD, 115K miles, never had issues until...

Last week my truck completely stalled on me after driving it w/no issues for about twenty minutes, but immediately stalled out at the gas station. Truck did the same thing after driving it on an hour long trip when i slowed down to about 20MPH on the freeway and RPM's were at about 1k. Had it towed to the closest shop and they informed me the fuel modulator kit was bad and that ended up costing me $800 out the door. I drove it back home on the freeway and it dies 2 more times getting off of the freeway.

There are no codes and the truck runs very well until it stalls out. The problems seems to only occur AFTER the truck has warmed up and I am decelerating, basically around 1k RPM. Took it back to the dealership and they swapped out the fuel pump kit AGAIN, thinking/hoping the last fuel pump kit was bad. That didn't work. They replaced the crankshaft sensor and that didn't change a thing. They also cleaned out the throttle body to no avail. They have also hooked up a fuel pressure meter to see if fuel is being starved prior to stalling out and they told me it drops to about 5 PSI before stalling.

Myself and the shop is completely dumbfounded and we're both scratching our heads. I wish the truck wasn't worth anything because I'd junk it and get another one, but it's gotta be fixable right?

I would appreciate any and everything you could add to this because I can't afford to dump anything more into it without knowing the issue. Thank you very much for any input!

rjgti · February 19, 2016

wow 5 psi and they have no clue, lmao

rjgti · February 19, 2016

that is returnless efi right, check pump pwm from ecm

GMSEEDENALI · February 19, 2016

Sorry I'm not much of a mechanic, but what would that entail?

rjgti · February 19, 2016

a scope for pwm or a tech2 for duty cycle

00Silverado4x4 · February 19, 2016

5 psi? There's the problem. I think you need to find a better dealership to fix your vehicle. If they didn't fix it right the first time, they should have warrantied their work. Obviously they are clueless wonders and you're footing the bill. I'd take that situation up their chain of command and get some real solutions.