Lack of Power/Sluggish/Spongy/Stumble

DEFINITION
Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is pushed down part way.

PRELIMINARY CHECKS
- Perform the careful visual / physical checks as described in Preliminary Checks.
- Compare customer's vehicle to similar unit. Make sure the customer has an actual problem.
- Remove air filter and check air filter for dirt, or for being plugged. Replace as necessary.
- Check the transmission shift pattern and down shift operation.
- If an injector is suspect on Central MFI engine, refer to Procedures / Diagnostic Charts / Chart A-7 Poppet Nozzle Diagnosis. Testing and Inspection

FUEL SYSTEM
- Check for contaminated fuel.
- Check for restricted fuel filter or improper fuel pressure, refer to Procedures / Diagnostic Charts / Chart A-6 Fuel System Diagnosis. Testing and Inspection

IGNITION SYSTEM
- Check ignition voltage output using a spark tester J 26792 (ST 125), or equivalent.
- Check ignition timing and proper operation of ignition control.

EXHAUST SYSTEM
- Check exhaust system for possible restriction, refer to Procedures / Diagnostic Charts / C Charts / Restricted Exhaust System Check. Testing and Inspection
- Inspect exhaust system for damaged or collapsed pipes. Inspect muffler for heat distress or possible internal failure.
1. With engine at normal operating temperature, connect a vacuum gage to any convenient vacuum port on intake manifold.
2. Operate engine at 1000 RPM and record vacuum reading.
3. Increase RPM slowly to 2500 RPM. Note vacuum reading at a steady 2500 RPM.
4. If vacuum at 2500 RPM decreases more than 10 kPa (3" Hg) from reading at 1000 RPM, the exhaust system should be inspected for restrictions.
5. Disconnect exhaust pipe from engine and repeat Steps 3 and 4. If vacuum still drops more than 10 kPa (3" Hg) with exhaust disconnected, check for exhaust manifold restriction and valve timing.

ADDITIONAL CHECKS
- Check PCM grounds for being clean, tight and in their proper locations. Refer to Engine Control Module / Diagrams.
- Check the Exhaust Gas Recirculation (EGR) operation for being open or partly open all the time. Refer to Procedures / Diagnostic Charts / C Charts / EGR System Check. Testing and Inspection
- Check Torque Converter Clutch (TCC) for proper operation.
- Check A/C operation.
- Check the generator output voltage. Repair if less than 9 or more than 16 volts.

ENGINE MECHANICAL
- Check Engine valve timing and compression.
- Check Engine for incorrect or worn camshaft.