Hesitation/Sag/Stumble

Symptom: 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

CHARGING SYSTEM MALFUNCTION - Check battery voltage.

- Check Generator voltage output.

IGNITION SYSTEM MALFUNCTION - Scope check Ignition System. Check SECONDARY CIRCUIT firing Kv and spark duration.
SEE IGNITION SYSTEM/OSCILLOSCOPE PATTERNS.

- Remove spark plugs and inspect for: cracks, excessive wear, improper gap, burned electrodes, and wet or heavy deposits. Replace as necessary.


- Inspect distributor cap, rotor and spark plug wires for proper plug wire routing, crossfire between spark plugs (in cap) or wires, wires shorting to ground and rotor shorting to ground via distributor shaft.

- Check IGNITION TIMING for excessive spark advance or retard.
SEE IGNITION SYSTEM/ TIMING SPECIFICATIONS

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 fuel pressure.

- Check for lean Air-Fuel mixture, (O2S Sensor output).

- Perform injector balance test.

- Check fuel quality.

- Check Throttle Position Sensor for proper operation.