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.


POSSIBLE CAUSE ACTION



Ignition System Malfunction Scope check Ignition System

Check IGNITION COIL for proper output voltage.

Check SPARK PLUGS for proper spark duration. Remove spark plugs, check for fuel fouled plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Replace as necessary.

Check SECONDARY CIRCUIT for abnormal firing Kv, crossfire between spark plugs (distributor cap, spark plug wires), and proper plug wire routing.

Check IGNITION TIMING for excessive spark advance or retard.



Engine Mechanical Malfunction Check COMPRESSION Perform a compression check, and cylinder leakage test, look for sticking or leaking valves.

Check for VACUUM LEAKS inspect Intake manifold, gasket(s), and hoses.



Fuel System Malfunction Check for incorrect Air-Fuel mixture, O2 Sensor, perform injector balance test, inspect regulator operation (check vacuum line and return hose), check fuel pressure.

Check Throttle Position Sensor for proper operation.

Check fuel quality.



Charging System Malfunction Check battery voltage.

Check Alternator voltage output.