Lack of Power/Sluggish/Spongy/Stumble
DEFINITIONEngine 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 Diagnosis By Symptom/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.
FUEL SYSTEM
Check:
^ Restricted fuel filter.
^ Fuel pressure, use Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures
^ Contaminated fuel.
BOOST CONTROL SYSTEM
Check Boost Control System components and connections. Use Chart C-18 Boost Control Solenoid Functional Check. Chart C-18 Boost Control Solenoid Functional Check
IGNITION SYSTEM
Check:
^ Secondary voltage using a spark tester J 26792 (ST 125), or equivalent, to check for a weak coil, testing one spark plug wire at a time.
^ Knock sensor system for false retard due to mechanical noise.
ADDITIONAL CHECKS
Check:
^ Powertrain Control Module (PCM) grounds for being clean, tight and in their proper locations.
^ Generator output voltage. Repair if less than 9 or more than 17.3 volts.
^ 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 muffler for heat distress or possible internal failure.
^ Shift solenoid system and Torque Converter Clutch (TCC) for proper operation. Refer to Chart C-8A [1][2]Torque Converter Clutch Functional Check. Chart C-8A Torque Converter Clutch (TCC) Functional Check
^ For PCM Diagnostic Trouble Code (DTC)P1568 or P1599 set. If so, vehicle may be operating in "Power Management" mode. Use DTC P1568 or P1599 for diagnosis in Diagnostic Trouble Code Charts/Diagnostic Trouble Codes P1568/P1599. P1568 P1599
ENGINE MECHANICAL
Check:
^ Engine valve timing and compression.
^ Engine for incorrect or worn camshaft.