Lack of Power/Sluggish/Spongy

SYMPTOM DESCRIPTION:

Engine delivers less than expected power. Little or no increase in speed, when accelerator is pushed down part way.

SYSTEM OR COMPONENT TO CHECK

COMPUTER INPUTS/OUTPUTS
CHECK:
FUEL INJECTION CONTROL UNIT: Defective or wrong control unit, check grounds for electrical integrity.
AIR MASS METER: Defective wiring or sensor.
OXYGEN SENSOR: Defective wiring or sensor
THROTTLE POSITION SENSOR: Improperly adjusted, damaged, or defective wiring

FUEL
CHECK:
FUEL PRESSURE: Check delivery pressure and volume output
FUEL INJECTORS: Check spray pattern, clogged or stuck.
CONTAMINATED FUEL: Water or diesel in fuel
RESTRICTED FUEL FILTER: Check delivery volume.
THROTTLE VALVE: Linkage incorrectly adjusted (throttle valve does not open fully).
TURBO SYSTEM: Bypass valve stuck open or low charge pressure, see FUEL SYSTEMS.

IGNITION
CHECK:
Proper ignition voltage output.

EXHAUST
CHECK:
RESTRICTION.
1. With engine at normal operating temperature, connect a vacuum gauge to any convenient vacuum port on intake manifold.
2. Run engine at 1000 rpm and record vacuum reading.
3. Increase rpm slowly to 2500 rpm. Note vacuum reading at a steady 2500 rpm.
4. If vacuum at 2500 rpm decreases more than 3" Hg, from reading at 1000 rpm, the exhaust system should be inspected for restrictions.
5. Disconnect exhaust pipe from engine and repeat Step 3 & 4. If vacuum still drops more than 3" Hg, with exhaust disconnected, check for exhaust manifold restriction and valve timing.

ENGINE/TRANSMISSION
CHECK:
BATTERY VOLTAGE: Check battery voltage and alternator output, A/C operation.
ENGINE COMPRESSION:
ENGINE VALVE TIMING:
ENGINE CAMSHAFT for wear and proper application.
TORQUE CONVERTER CLUTCH: Check operation.
TRANSMISSION SHIFT POINTS:
CLUTCH OPERATION: Worn or damaged clutch disc or pressure plate