Truck accelerates on its own

[Heavy 5.7]

Have you already tried using smoke/propane/carb cleaner to locate a leak? (this would have confirmed an actual intake manifold gasket leak)

I'll assume the throttle valve was removed for cleaning, did you use a new identical gasket when reinstalling?

Did you inspect the throttle shaft for binding and excessive play?

Are the cables leading to the throttle body correctly routed and not binding?

When the vehicle is accelerating "on it's own" can you lift the accelerator pedal with your foot and slow it down?

[Rgbraun1]

Heavy5.7,

I tried the carb cleaner/vacuum leak test but couldn't find anything. Can't get to the "inside" edge if the intake manifold to spray it though. The Chevy tech guy at the dealership said it was the intake manifold gasket. I replaced it myself with the new heavy duty Fel-Pro. Throttle linkage had no play, throttle cable/ cruise cable seem fine. I tried lifting the gas pedal as it accelerates on its own and it didn't do anything. I've pulled the cruise control fuse to make sure that wasn't it. I've put about 200 miles on it since all the work and it accelerated on its own out of the driveway....and hasn't really done it since. It is holding speed/ not decelerating as quickly as it used to.

[Heavy 5.7]

Any stored codes now? If the the cables and linkage are not binding and the engine is still gaining speed "on it's own" it has to be due to a vacuum leak.

[Rgbraun1]

No stored codes. The acceleration problem seems to have diminished since i replaced the intake manifold gasket. It's still there, but not as bad as it was. I replaced the PCV grommet. I'm wondering if the grommet and valve at the brake booster is leaking. Also, wondering about the fuel purge valve solenoid. It sits on top of the intake manifold and sits up a little high. I can see it taking some unintended abuse as I worked on the TB originally and now especially since I had the intake manifold off and sitting upside down as I cleaned it.

[Heavy 5.7]

If the battery was disconnected prior to repairs give it some time/miles to settle in & see what happens.