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". Testing and Inspection
^ 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.

IGNITION SYSTEM
^ Check knock Sensor (KS) system for excessive spark retard activity. Refer to "DIAGNOSTIC CHARTS/C-CHARTS/CHART C-5 KNOCK SENSOR (KS) SYSTEM CHECK". Chart C-5 Knock Sensor (KS) System Check
^ Check secondary voltage using a spark tester J-26792 (ST-125) or equivalent to check for a weak coil.
^ Check spark advance for excessive retarded ignition timing. Refer to "DIAGNOSTIC CHARTS/C-CHARTS/CHART C-5 KNOCK SENSOR (KS) SYSTEM CHECK". Chart C-5 Knock Sensor (KS) System Check

ENGINE MECHANICAL
^ Check engine valve timing and compression.
^ Check engine for correct or worn camshaft.

FUEL SYSTEM
^ Check for restricted fuel filter.
^ Check fuel pressure. Refer to "DIAGNOSTIC CHARTS/A-CHARTS/CHART A-7 FUEL SYSTEM DIAGNOSIS". Related Tests, Information and Procedures
^ Check for contaminated fuel.

ADDITIONAL CHECKS
^ Check PCM grounds for being clean, tight and in their proper locations. See PCM wiring diagrams.
^ Check Torque Converter Clutch (TCC) for proper operation. Refer to "DIAGNOSTIC CHARTS/C-CHARTS/CHART C-8 TRANSMISSION DIAGNOSIS". Chart C-8 Transmission Diagnosis
^ Check alternator output voltage. Repair if less than 9 or more than 16 volts.
^ Check A/C operation. A/C clutch should cut out at Wide Open Throttle (WOT). Refer to "DIAGNOSTIC CHARTS/C-CHARTS/CHART C-10 A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS". Chart C-10 A/C Clutch Control Circuit Diagnosis
^ Check Exhaust system for possible restriction. Inspect exhaust system for damaged or collapsed pipes, heat distress, or plugged catalytic converter. Refer to "DIAGNOSTIC CHARTS/CHART B-1 RESTRICTED EXHAUST SYSTEM CHECK. B Charts