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 for being plugged.

- Check the transmission shift pattern and down shift operation.

- Check for fuel injector. Refer to Fuel Injector Coil Test/Fuel Injector Balance Test Procedure.
Fuel Injector Balance Test

Fuel System Checks

- Check for a restricted fuel filter, contaminated fuel or improper fuel pressure. Refer to "Table A-7B." Table A-7B Fuel System Diagnosis (Fuel Pressure Check)

- Check for contaminated fuel.

Ignition System Checks

- Check for the proper ignition voltage output with the spark tester J 26792 or equivalent.

- Check the ignition timing and proper operation of the ignition control system.

Exhaust System Checks

- Check the exhaust system for a possible restriction: Refer to the appropriate service manual.

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

Additional Checks

- Check the ECM grounds for being clean, tight, and in their proper location. Refer to Starting and Charging / Power and Ground / Locations.

- Check the EGR Valve for being open or partly open all the time.

- Check the generator output voltage.

Engine Mechanical Check

- Check the engine for the following:

- Compression

- Valve timing

- Proper or worn camshaft

- Refer to the appropriate service manual.