Stalling on start up

[grasshopper]

I have a 2000 K2500 LQ4 Suburban with the following problem:

 

Occasionally the truck will start and stall as soon as the key is released. The engine does not seem to go through it's normal acceleration and decceleration back to idle. When the problem occurs, if you apply a small amout of throttle (700 RPM), the engine will stay running. If this throttle is released the engine will stop. After about 2 minutes with the throttle at 700 RPM, or above, the engine will then stay running. The MIL has not illuminated. The ECT, TP sensor and PCM connections have been checked for cleanliness and a connectivity. This can occur on a warm or cold engine start, with the fuel tank full or near empty.

 

The engine was overhauled, 4000 miles ago, for piston slap. Yes the General paid for it! The truck now has 63,000 miles on it. This problem has just started in the last 1,000 miles.

 

Any help would be appreciated.

 

Cheers,

 

Butch