For 1990-2009 cars

## Hesitation, Sag, Stumble Petrol

Checks | Action
--- | ---
DEFINITION: The vehicle has a momentary lack of response when depressing the accelerator pedal. The condition can occur at any vehicle speed. The condition is usually most severe when attempting to make the vehicle move, as from a stop sign. An extremely severe condition may cause the engine to stall.
Preliminary Checks | Refer to Important Preliminary Checks in Symptoms - Engine Controls .
Fuel System Checks |

• | Test for correct fuel system pressures. Refer to Fuel System Diagnosis .

| Inspect for low pressure during moderate or full throttle acceleration. If the fuel pressure drops below specification, there is possibly a low or regulator fault or a fuel system restriction.

• | Test for correct EVAP purge system operation.

Sensor Checks |

• | Test for correct TP sensor operation. A TP sensor that does not respond quickly and accurately to throttle plate movement may cause this symptom.

• | Test for correct MAP sensor operation. A MAP sensor that does not respond quickly and accurately to manifold pressure changes may cause this symptom.

Ignition System Checks |

• | Inspect for fouled spark plugs.

| If fouled spark plugs are indicated the reason for the fouling must be found and corrected.

• | Test for faulty spark plug wires.

• | Test for an open ignition system ground.

Additional Checks |

• | Review service bulletins for module programming updates.

• | Inspect for manifold or air induction system leaks.

• | Test for correct generator operation.