Surges/Chuggles

Surges and/or Chuggles

Definition: Engine power variation, under steady throttle or cruise. Feels like the vehicle speeds up and slows down, with no change in the accelerator pedal.

Preliminary Checks

- Refer to Diagnostic System Check, Testing and Inspection
- Be sure driver understands Torque Converter Clutch (TCC) and A/C compressor operation in owners manual.
- Check speedometer reading with the speed on a scan tool are equal.
- Check for service bulletins for updates.

Sensors

- Check oxygen sensor (O2S). The oxygen sensor should respond quickly to different throttle position, if it does not, check the oxygen sensor for silicon or other contaminations 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, causeing a severe driveability problem. Also, check for green (glycol) contamination or cracking.

Fuel System

- Check to determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring fuel trim will help identify a problem.
- Lean - Long term fuel trim greater than 150
- Rich - Long term fuel trim less than 115.
- Check fuel pressure while condition exists.
- Check in-line fuel filter. Replace if dirty or plugged.
- Check fuel injectors. Perform injector balance test. Use chart A7.

Ignition System

- Check for proper ignition voltage output using spark tester J 26792 or equivalent.
- Check spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
- Check ignition timing,

Additional Checks

- Control module grounds for being clean, tight, and in their proper locations.
- Check generator output voltage. Repair if less than 9 or more than 16 volts.
- Check vacuum lines for kinks or leaks.
- Check for intermittent EGR.
- Check for TCC operation.
- Check 4 wheel drive low switch operation.