Hesitation/Sag/Stumble

SYMPTOM DESCRIPTION:

Momentary lack of response when the accelerator is pushed down. Can occur at any speed. Usually most severe from a stop or initial take off. Engine may stall if condition is bad enough.




SYSTEM OR COMPONENT TO CHECK ACTION

COMPUTER INPUTS/OUTPUTS CHECK: - THROTTLE POSITION SENSOR (TPS)
Check for binding or sticking. Voltage should
increase smoothly as the throttle valve is
opened to Wide Open.
- MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
Test sensor response and accuracy,
refer to COMPONENT TEST PROCEDURES.



FUEL CHECK: - FUEL PRESSURE

- WATER CONTAMINATED FUEL



IGNITION CHECK: - For defective plug wires.
- For fouled spark plugs.
- Open ignition system ground.
- Ignition timing.



EMISSIONS CHECK: - EGR SYSTEM:
Valve or Solenoid operation.
- EVAPORATIVE SYSTEM
Canister Purge System operation.
Refer to Powertrain Management/Emission Control Systems/Testing and Inspection/Procedures.




ENGINE CHECK: - ALTERNATOR
Verify output voltage. Inspect for bad diodes.
Repair of replace if output voltage is
less than 9 or greater than 16 volts.