Hesitation, Sag, Stumble

Checks	Action
DEFINITION: The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur at any vehicle speed. The condition is usually most severe when trying to make the vehicle move from a stop. The condition may cause the engine to stall if it is severe enough.
Preliminary Check	Refer to Symptoms - Engine Controls .
Fuel System Checks	Check the fuel pressure. Refer to Fuel System Diagnosis . Check for water contamination in the fuel. Refer to Contaminants-in-Fuel Diagnosis . Perform the Injector Balance Test. Check for low fuel pressure after a cold start or during moderate or full throttle acceleration. If fuel pressure drops below specification, there is possibly a malfunctioning fuel pump or a restriction in the fuel system.
Additional Checks	Check the service bulletins for control module software updates. Check the generator output voltage.