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 or 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.



EMISSIONS COMPONENT MALFUNCTION - Check EGR valve for premature opening.

- Check EGR Transducer for proper operation.



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.