Surges and/or Chuggles

DEFINITION
Engine power variation, under steady throttle or cruise. Feels like the car speeds up and slows down, with no change of the accelerator pedal.

Use a "Scan' tool to make sure reading of VSS matches vehicle speedometer.

CHECK:
- Throttle linkage for interference and proper travel.
- Vacuum hoses for splits, kinks and proper connections.
- For intermittent EGR at idle.
- Ignition timing. See Emission Control Information label.
- Inline fuel filter for dirt or restriction.
- Fuel pressure.
- Alternator output voltage. Repair, if less than 9, or more than 16 volts.
- Poor or contaminated gasoline. Excessive alcohol content, suggest owner try different brand.

Inspect oxygen sensor for silicone contamination from fuel, or use of improper RTV sealant. The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.

Remove spark plugs. Check for cracks, wear, improper gap, burned electrodes, or heavy deposits. Also, check condition of the rest of the ignition system.