Engine Runs Rough Or Stalls At Idle - keywords canister emissions engine evap fuel full grade idle intermittent module runs rough sending stall tank unit valve vent

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may comment that the engine intermittently runs rough or stalls at idle. Others may comment that the condition only occurs when the fuel tank is full.

Inspect the Evaporative Emissions Canister for evidence of fuel. If fuel is found, remove the fuel tank and inspect the fuel tank module for the presence of the Grade Vent Valve. If the Grade Vent Valve is missing it will be necessary to replace the complete fuel tank sending unit module. It will also be necessary to replace the Evaporative Canister.

Important: The Grade Vent Valve is NOT serviced separately. To obtain one you must install a new fuel tank sending unit module. See the appropriate section of the GMSPO parts catalog for fuel tank sending unit module part numbers and usages.

This illustration shows the grade vent valve missing.

This illustration shows the grade vent valve in place.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.