Surges/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
- Perform the careful "Visual And Physical Checks" in Preliminary Checks. Testing and Inspection
- Be sure driver understands Torque Converter Clutch (TCC) and A/C compressor operation described in Owner's Manual.

SENSORS
- Check Mass Air Flow (MAF) sensor response and accuracy.
- Check Heated Oxygen Sensor (HO2S) for silicon contamination from fuel, or use of improper RTV sealant. The HO2S 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.

FUEL SYSTEM

NOTE: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Using a Tech 1 scan tool to monitor HO2S voltage will help identify a problem.
Lean - HO2S voltage below 450 mV
Rich - HO2S voltage above 450 mV

- Check fuel pressure while condition exists.
- Check in-line fuel filter. Replace if dirty or plugged.

IGNITION SYSTEM
- Check for proper ignition output voltage using 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.

ADDITIONAL CHECKS
- Check ECM grounds for being clean, tight, and in their proper locations.
- Check generator output voltage.
- Check vacuum hoses for kinks or leaks.
- Check for intermittent EGR at idle, refer to Chart C-7A EGR System Check. Chart C-7A Exhaust Gas Recirculation (EGR) Check
- Check TCC operation, refer to Chart C-8A Torque Converter Clutch (TCC) Relay System Check. Chart C-8A Torque Converter Clutch (TCC) Relay System Check
- Check speedometer for correct operation (fluctuating needle, speedometer cable for restricted movement, damaged cable).