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 check 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.

FUEL SYSTEM
Check:
Restricted fuel filter.
Fuel pressure, use Chart A-7. Testing and Inspection
Contaminated fuel. Verify proper fuel usage with manufacturer recommended minimum rating of 91 octane.

IGNITION SYSTEM
Check:
Knock Sensor (KS) system for excessive spark retard activity. Refer to Chart C-5. Use Tech 1. Testing and Inspection
Secondary voltage using a spark tester J 26792 (ST 125) or equivalent to check for a weak coil.

ADDITIONAL CHECKS
Check:
Powertrain Control Module (PCM) grounds for being clean, tight and in their proper location. Refer to PCM wiring diagram.
Generator output voltage. Repair if less than 9 or more than 17.3 volts.
Exhaust system for possible restriction.
- Inspect exhaust system damage or collapsed pipes.
- Inspect mufflers for heat distress or possible internal failure.
- For possible plugged three-way catalytic converters by comparing exhaust system back pressure on each side of engine. Check back pressure by removing Bank 2 Heated Oxygen Sensor (HO2S).

EGR operation for being open or partly open all the time. Use Chart C-7. Testing and Inspection
Air induction system for restriction or leaks.
Proper transaxle operation, TCC and shift solenoids.

ENGINE MECHANICAL
Check:
Engine valve timing and compression.
Engine for correct or worn camshaft(s).