GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Geo 🢒 1997 🢒 Prizm 🢒 Engine 🢒 Engine Controls - 1.6L 🢒 Hesitation, Sag, Stumble

Hesitation, Sag, Stumble

Checks

Action

DEFINITION: The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur at any vehicle speed. The condition is usually most severe when trying to make the vehicle move, as from a stop sign. The condition may cause the engine to stall if severe enough.

Preliminary Check
    • Refer to Symptoms.

Fuel System Checks
    • Check for a restricted fuel filter or incorrect fuel pressure. Refer to Fuel System Diagnosis.
    • Check the fuel injectors. Perform the Fuel Injector Coil Test Procedure and the Fuel Injector Balance Test Procedure. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and Fuel Injector Balance Test.
    • Check for water contamination of the fuel.
    • Check the TP sensor for binding or sticking. Voltage should increase at a steady rate as throttle moves toward Wide Open Throttle (WOT).
    • Check the MAP sensor for a quick response and accuracy.
    • Check the Evaporative Emission (EVAP) control system. Refer to Evaporative Emission Control System Diagnosis.

Ignition System Checks
    • Check for faulty spark plug wires.
    • Check for fouled spark plugs.

Additional Checks
    • Inspect for the correct operation of the exhaust gas recirculation (EGR) system. An inoperative EGR system can cause excessive detonation that results in retarded ignition timing. Excessive EGR flow can cause incorrect air fuel ratios resulting in inefficient combustion.. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis.
    • Check the Service Bulletins for any updates.
    • Check the generator output voltage.