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 visual and physical checks as described in Preliminary Checks.
^ Compare customer's vehicle to similar unit. Make sure the customer has an actual problem.
^ Remove and check air filter for dirt, or for being plugged. Replace as necessary.

FUEL SYSTEM
Check: Restricted fuel filter.

Check: Fuel pressure. Refer to Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures

Check: Contaminated fuel.

IGNITION SYSTEM
Check: Knock Sensor (KS) system for excessive spark retard activity. Refer to Chart C-5 Knock Sensor System Check. Use Tech 1 scanner.

Check: Secondary voltage using a shop oscilloscope or a spark tester J26792 (ST 125), to check for a weak coil.

Check: Distributor vent system. Refer to Chart C-4C Distributor Vent System Check. Chart C-4C Distributor Vent System Check

Check: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

ADDITIONAL CHECKS
Check: Powertrain Control Module (PCM) grounds for being clean, tight and in their proper locations. Refer to Diagrams under Computer and Control Systems.

Check: EGR operation for being open or partly open all the time. Use Chart C-7 EGR System Check. Chart C-7 Exhaust Gas Recirculation (EGR) System Check

Check: Generator output voltage. Repair if less than 9 volts or more than 16 volts.

Check: Exhaust system for possible restriction. Refer to Chart B-1 Restricted Exhaust System Check. B Charts

- Inspect exhaust system for damaged or collapsed pipes.
- Inspect mufflers for heat distress or possible internal failure.
- For possible plugged three-way catalytic converters by comparing exhaust system backpressure on each side of engine. Check backpressure by removing Air Injection Reaction (AIR) check valves near exhaust manifolds.

Check: Throttle cable system cable adjuster assembly. Loss of performance can result from an improperly adjusted system which could prevent the throttle from attaining Wide Open Throttle (WOT).

Check: Torque Converter Clutch (TCC) for proper operation.

Check: PROM Calibration I.D. for most current and/or incorrect software. Refer to PROM - Programmable Read Only Memory.

ENGINE MECHANICAL
Check: Engine valve timing and compression.

Check: Engine for correct or worn camshaft.