Lly duramax rough idle in park
Devilbiss tekna cup
x2 on the fuel pressure regulator,that will cause an erratic idle, if the fuel pressure relief valve goes bad the vehicle will fall flat under hard acceleration.
The first feature of the High Idle is designed to increase the RPM of the Duramax Truck. While the engine is running, and in park, the cruise control device can be switched on and the engine will begin to increase the RPM to 1,200.