Surges at Steady Speed

Definition
Engine power variation under steady throttle or cruise. Feels like the car speeds up and slows down with no change in accelerator pedal.

POSSIBLE CAUSE ACTION

Lean operating condition NOTE To determine if the condition is caused by
a lean or rich system, drive vehicle at
speed of complaint and monitor fuel trim.

Check Air/fuel ratio (O2 Sensor Voltage)
Perform Oxygen Sensor Test in DIAGNOSIS, TESTING AND
INSPECTION PROCEDURES in
COMPUTERS AND CONTROL SYSTEMS





Insufficient fuel delivery Check - Fuel pressure/ regulator.
- Fuel filter/ hose or line restriction
Repair/Replace As required





Leaking/Inoperative fuel injector(s) Check Injector(s).
Perform: - Injector driver circuit test.
- Injector balance test.
- Injector service (cleaning)



Contaminated fuel Check Water or excessive alcohol in fuel.
Replace Drain fuel tank and add clean fuel



Vacuum leak Check - Intake manifold surface and gasket
- Throttle body base surface and gasket