Surges/Chuggles

Symptom: Engine power variation under steady throttle or at cruise. Feels like the vehicle speeds up and slows down, with no movement of the accelerator pedal.

POSSIBLE CAUSE ACTION

CHARGING SYSTEM MALFUNCTION - Check battery voltage.

- Check generator output voltage.

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 spark plug wires for proper plug wire routing, crossfire between spark plugs or wires shorting to ground.

- Check IGNITION TIMING for excessive spark advance or retard.
SEE Powertrain Management/Ignition System/Specifications.


ENGINE MECHANICAL MALFUNCTION - Perform compression and cylinder leak down 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 binding or sticking in the open position.

- Check EGR Transducer for proper operation.

- Check Evaporative control system.

FUEL SYSTEM MALFUNCTION - Check fuel pressure.

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

- Perform injector balance test.

- Check fuel quality.