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 acceleration pedal.

PRELIMINARY CHECKS
^ Perform the careful visual / physical checks as described in Preliminary Checks.
^ Be sure driver understands transmission [1][2]torque converter clutch, and A/C compressor operation as explained in the owners manual.
^ Use a scan tool to make sure reading of Vehicle speed Sensor (VSS) matches vehicle speedometer except vehicles with electronic transmissions where some variation between VSS and speedometer is normal. Refer to Procedures / Diagnostic Charts / Code 16 Vehicle Speed Sensor Buffer Fault. Testing and Inspection

SENSORS
^ Check the Heated Oxygen Sensor (HO2S). The heated oxygen sensor should respond quickly to different throttle positions; if it does not, check the heated oxygen sensor for silicon or other contaminants from fuel or use of improper RTV sealant. The sensor may have a white, powdery coating and a high but false signal voltage (rich exhaust indication). The Powertrain Control Module (PCM) will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Also, watch for green glycol contamination or cracking.

FUEL SYSTEM
^ 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. Refer to Procedures / Diagnostic Charts / Code 44 Oxygen Sensor Circuit, "Diagnostic Aids". Testing and Inspection
Rich - Long term fuel trim less than 115. Refer to Procedures / Diagnostic Charts / Code 45 Oxygen Sensor Circuit, "Diagnostic Aids". Testing and Inspection
^ Check the fuel pressure while condition exists, refer to Procedures / Diagnostic Charts / Chart A-6 Fuel System Diagnosis. Testing and Inspection

IGNITION SYSTEM
^ Check for adequate ignition voltage output using spark tester J 26792 (ST 125) or equivalent.
^ Check the spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary. Also, check condition of spark plug wires.
^ Check the ignition timing.

ADDITIONAL CHECKS
^ Check PCM grounds for being clean, tight and in their proper location.
^ Check the Generator output voltage. Repair if less than 9 or more than 16 volts.
^ Check Vacuum lines for kinks or leaks.
^ Check for intermittent Exhaust Gas Recirculation (EGR). Refer to Procedures / Diagnostic Charts / C Charts / EGR System Check. Testing and Inspection
^ Check the [1][2]Torque Converter Clutch (TCC) operation.