Lack of Power/Sluggish/Spongy/Stumble

Definition
The engine delivers less than expected power, or little increase in vehicle speed when the accelerator pedal is depressed.

Preliminary Checks
^ Perform the visual/physical checks as described under Diagnostic Notes in this section.
^ Compare customers vehicle to similar vehicle. Verify symptom.
^ Remove air filter and check air filter for dirt, or for being plugged. Replace as necessary.

Fuel System
^ CHECK: Fuel pressure.
^ CHECK: Restricted fuel filter.
^ CHECK: Contaminated fuel.

Ignition System
^ CHECK: Ignition timing. See "Vehicle Emission Control Information" label.
^ CHECK: Secondary voltage using J26792 or equivalent, to check for a faulty ignition coil.

Additional Checks
^ CHECK: ECM/PCM grounds for being clean, tight and in their proper locations. See ECM/PCM wiring diagrams.
^ CHECK: Generator output voltage. Repair if less than 12 or more than 16 volts.
^ CHECK: A/C operation. A/C compressor clutch should cut out at wide open throttle (WOT).
^ CHECK: Exhaust system for possible restriction.
- inspect exhaust system for damaged or collapsed pipes.
- Inspect muffler for heat distress or possible internal failure.
- For possible plugged three-way catalytic converter (TWC) or warm up three-way catalytic converter (WU-TWC).
^ CHECK: Torque Converter Clutch (TCC) for proper operation.
^ CHECK: EGR operation for being open or partly open all the time (California Emissions only).

Engine Mechanical
^ CHECK: Engine valve timing and compression.