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:

- CONTROL UNIT: Poor connections, damaged wiring, defective or wrong control unit. Check all electrical ground circuits for good connections.
- AIR FLOW SENSOR AND CO POTENTIOMETER: Defective sensor or improper CO adjustment. Poor connections or damaged wiring to control unit.
- THROTTLE SWITCHES: Improperly adjusted, poor connection or damaged wiring to control unit, or defective switch.
- COOLANT TEMPERATURE SENSOR: Poor connection, damaged wiring to control unit, or defective sensor.
- TEMPERATURE SAFETY SWITCH (MULTIFUNCTION TEMPERATURE SENSOR): [1] Defective switch or wiring.
- WASTEGATE FREQUENCY VALVE: [1] Inoperative or defective valve, poor connections or damaged wiring to control unit.

[1] Turbocharged models only.



FUEL SYSTEM

CHECK:

- FUEL PRESSURE: Check delivery pressure and volume output from fuel pump. Check system pressure and control pressure.
- FUEL INJECTORS: Check spray pattern,
- FUEL DISTRIBUTOR: Sticking control plunger, incorrect basic air/fuel ratio (check idle CO content).
- CONTAMINATED FUEL: Water or diesel in fuel
- RESTRICTED FUEL FILTER: Check delivery pressure and volume.



IGNITION SYSTEM

CHECK:

- KNOCK SENSOR: Defective sensor, dirt between mating surfaces.
- IGNITION TIMING: Check distributor basic adjustment.
- IGNITION DISTRIBUTOR, CAP, AND ROTOR: Check for cracks, arcing, moisture, rust deposits or high resistance through rotor.




EXHAUST SYSTEM

CHECK:

- EXHAUST 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/or incorrect valve timing.

TURBO MODELS:

- Check turbocharger mechanical condition. Turbine and impeller should spin freely and without bearing noise.
- Check wastegate for sticking or binding. Check vacuum/pressure hoses for cracks, splits, pinches, or improper connections.




ENGINE/TRANSMISSION

CHECK:

- ENGINE COMPRESSION:
- ENGINE CAMSHAFT: Check for worn cam lobes &/or incorrect valve timing.
- TORQUE CONVERTER CLUTCH: Check operation.
- TRANSMISSION SHIFT POINTS:
- CLUTCH OPERATION: Worn or damaged clutch disc or pressure plate.



Also see Audi TSB #289003, #259102.