Engine Control System & Fuel System - Diagnosis & Troubleshooting: Surges/Chuggles

Surges and/or Chuggles Symptom

Checks	Action
DEFINITION: The engine has a power variation under a steady throttle or cruise. There is a feeling as if the vehicle speeds up and slows down with no change in the accelerator pedal.
Preliminary Checks	Refer to Diagnostic System Check - Vehicle . Refer to Symptoms - Engine Controls . Be sure the driver understands the A/C compressor operation. Use a scan tool to make sure the reading of the vehicle speed sensor (VSS) matches the reading of the instrument panel speedometer. Transmission performance can be affected by incorrect VSS readings. If accuracy of the VSS is a concern, refer to Speedometer and/or Odometer Inaccurate or Inoperative .
Sensor Checks	Check the heated oxygen sensors (HO2S) 1 and HO2S 2 performance. Refer to the Diagnostic Aids for DTC P2195 . Inspect the mass air flow (MAF) sensor operation. Run the engine to normal operating temperature. Turn OFF all accessories and observe the MAF sensor at idle with a scan tool. If the MAF sensor reading is more than 3.5 g/s refer to DTC P0101 . Check for correct operation of the engine coolant temperature (ECT) sensor. A fixed or inaccurate ECT sensor reading can cause the engine to surge, especially at low speeds and at stops.
Fuel System Checks	Determine if a rich or lean system can cause the condition. Drive the vehicle at the speed of the complaint. Monitoring the Fuel Trim may help identify the problem. Lean-The Long Term Fuel Trim will be more than 20 percent. Refer to Diagnostic Aids in this test. Rich-The Long Term Fuel Trim will be less than -20 percent. Refer to Diagnostic Aids in this test. Check the fuel injectors. Perform the following procedures: The Fuel Injector Coil Test-Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) or to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F) . The Fuel Injector Balance Test-Refer to Fuel Injector Balance Test with Special Tool . Check the fuel pressure while the condition exists. Refer to Fuel System Diagnosis .
Ignition System Checks	Check for the proper secondary voltage output with a J 26792 Spark Tester. Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection .
Additional Checks	Check the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics . Inspect the positive crankcase ventilation (PCV) valve for correct operation and the correct part. Refer to Crankcase Ventilation System Inspection/Diagnosis . Check the generator for the correct output voltage. Check the vacuum lines and hoses for leaks or incorrect routing. Refer to Emission Hose Routing Diagram and Evaporative Emissions Hose Routing Diagram . Inspect for correct operation and correct shifting of the transmission. Inspect for correct engagement of the torque converter clutch (TCC) Symptoms - Automatic Transmission .