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 as described in Preliminary Checks. Testing and Inspection

^ Be sure driver understands [1][2]Torque Converter Clutch (TCC) and A/C compressor operation in owner's manual.
^ Use a scan tool to make sure reading of Vehicle Speed Sensor (VSS) matches vehicle speedometer.

SENSORS
Check: Oxygen Sensor (O2S) for silicon 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 (high O2S signal). The Engine Control Module (ECM) will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.

FUEL SYSTEM
To determine if the condition is caused by a rich or lean 02S signal, the vehicle should be driven at the speed of the complaint. Monitoring long term fuel trim will help identify a problem.

Lean - Long term fuel trim greater than 150. Refer to "Diagnostic Aids" in Diagnostic Trouble Code (DTC) 44. Powertrain Controls - ECM/PCM

Rich - Long term fuel trim less than 115. Refer to "Diagnostic Aids" in DTC 45. Powertrain Controls - ECM/PCM

Check: Fuel pressure while condition exists. Refer to Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures

Check: In-line fuel filter. Replace if dirty or plugged.

ADDITIONAL CHECKS
Check: ECM grounds for being clean, tight, and in their proper locations.

Check: Generator output voltage. Repair if less than 9 volts or more than 16 volts.

Check: Vacuum lines for kinks or leaks.

Check: For intermittent EGR at idle. Refer to Chart C-7 Exhaust Gas Recirculation Check. Chart C-7 EGR System Check

Check: TCC operation. Refer to Chart C-8 [1][2]Torque Converter Clutch System. Chart C-8 Torque Converter Clutch (TCC) Diagnosis