Lack of Power/Sluggish/Spongy/Stumble

Definition: The engine delivers less than expected power. There is little or no increase in speed when partially applying the accelerator pedal.

Preliminary Checks

^ Refer to Important Preliminary Checks. Testing and Inspection
^ Compare the customer's vehicle with a similar unit. Make sure the customer has an actual problem.
^ Remove the air filter and check for dirt or a restriction.
^ Check the transmission shift pattern and the downshift operation.

Fuel System Checks

^ Check for a restricted fuel filter, contaminated fuel, or improper fuel pressure. Refer to Fuel System Pressure Test. System Diagnosis - Fuel System Pressure Test
^ Perform the fuel injector balance test. Refer to Fuel Injector Balance Test. Fuel Injector Balance Test
^ Check for the proper ignition output voltage with the spark tester J 26792 or the equivalent.
^ Check the Knock Sensor (KS) system. Refer to Knock Sensor System Diagnosis. System Diagnosis - Knock Sensor (KS)

Exhaust System Checks

^ Check the exhaust system for a possible restriction.
^ Inspect the exhaust system for damaged or collapsed pipes. Inspect the muffler for heat distress or a possible internal failure.

Additional Checks

^ Check the Control Module grounds for being clean, tight, and in their proper location.
^ Check the Exhaust Gas Recirculation (EGR) Valve for being open or partially open all the time. Refer to EGR System. System Diagnosis - EGR
^ Check the Torque Converter Clutch (TCC) operation.
^ Check the A/C operation. Refer to A/C Compressor Clutch Control Diagnosis. A/C Compressor Clutch Control Diagnosis
^ Check the generator output voltage.

Engine Mechanical Check

^ Check the engine for the proper operation of the following items:

^ Engine compression.
^ Valve timing.
^ Improper or worn camshaft. Refer to Engine.