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 at a steady rate as throttle is moved
toward Wide Open Throttle (WOT).
- MANIFOLD ABSOLUTE PRESSURE SENSOR
(MAP): Sensor response and accuracy.





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 operation.
- EVAPORATIVE SYSTEM: Cannister purge system
operation.
NOTE: Refer to EMISSION CONTROLS for testing procedures.





ENGINE CHECK: - Generator output voltage. Repair, if less
than 9 or greater than 16 volts.