Lack of Power/Sluggish/Spongy/Stumble
DEFINITIONEngine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.
PRELIMINARY STEPS
^ Refer to Important Preliminary Checks and Visual and Physical Checks before starting.
^ Search for Technical Service Bulletins.
^ Check PCM grounds for being clean, tight and in their proper locations. Refer to Diagrams / Powertrain Control Module for PCM ground numbers and locations.
^ Remove and check air filter element for dirt, or for being restricted and replace as necessary.
FUEL SYSTEM CHECKS
^ Check for low fuel pressure. Refer to Fuel System Diagnosis.
^ Check for restricted fuel filter. Refer to Fuel System Diagnosis.
^ Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test.
^ Check items which can cause an engine to run rich (long term fuel trim near -14%). For a rich condition, refer to DTCs:
P0132 HO2S Circuit High Voltage Bank 1 Sensor 1
P0152 HO2S Circuit High Voltage Bank 2 Sensor 1.
^ Check items that can cause an engine to run lean (long term fuel trim near 22%). For a lean condition, refer to DTCs:
P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1.
SENSOR/SYSTEM
^ Using a scan tool, monitor Knock Sensor (KS) system for excessive spark retard activity. Refer to Knock Sensor / Testing and Inspection.
IGNITION SYSTEM
^ Wetting down the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look/Listen for arcing or misfiring as water is applied.
^ Check for proper ignition voltage output with spark tester J 26792. Refer to Ignition System / System Diagnosis for procedure.
^ Remove spark plugs and check for the following:
- Wet plugs
- Cracks
- Wear
- Improper gap
- Burnt electrodes
- Heavy deposits
^ An improper spark plug gap will cause a driveability problem. Refer to Spark Plug / Specifications for spark plug gap.
The spark plug gapping should be done using a wire gauge gap tool (J 41319). Refer to Spark Plug / Service and Repair for replacement procedures.
^ If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. To diagnose the rich condition, refer to DTCs:
P0172 Fuel Trim System Rich Bank 1
P0175 Fuel Trim System Rich Bank 2
^ Refer to Engine / System Diagnosis for the oil fouling condition.
^ Check for loose ignition coil ground. Refer to Distributor Ignition System Check.
^ Spark plugs for proper heat range. Refer to Owner's Manual or Spark Plugs / Application and ID.
^ Check distributor vent system for being restricted or open. Refer to Distributor Vent System Check.
ENGINE MECHANICAL
^ Excessive oil in combustion chamber-Leaking valve seals. Refer to Engine / System Diagnosis.
^ Low cylinder compression. Refer to Engine / System Diagnosis.
^ For incorrect basic engine parts. Inspect the following:
- Camshaft
- Cylinder heads
- Pistons, etc.
Refer to Engine.
ADDITIONAL CHECKS
^ Check exhaust system for possible restrictions. Check for the following:
- 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 back pressure on each side of engine. Check back pressure by removing Secondary Air Injection (AIR) check valves near exhaust manifolds. Refer to Restricted Exhaust System Check.
^ Check Torque Converter Clutch (TCC) operation. Refer to Transmission and Drivetrain / Automatic Transmission/Transaxle / Torque Converter Clutch.
^ Throttle Cable (TC) 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). Refer to Fuel Delivery and Air Induction / Throttle Cable. Also inspect the throttle body and accelerator cables for binding.