Surges/Chuggles

Definition: The engine has a power variation under a steady throttle or cruise. The vehicle feels as if it speeds up and slows down with no change in the accelerator pedal.

Preliminary Checks

^ Refer to "Important Preliminary Checks." Testing and Inspection

^ Be sure the driver understands the A/C compressor operation.

^ Use the scan tool to make sure the reading of Vehicle Speed Sensor (VSS) matches vehicle speedometer. This excludes vehicles with electronic transmissions where some variation between VSS and the speedometer is normal. Refer to DTC P0500 "Diagnostic Aids." Testing and Inspection

Sensor Check

^ Check the Heated Oxygen Sensor (HO2S 1) performance. Refer to DTC P0130, P0136. Testing and Inspection

Fuel System Checks

^ Check to determine if a Rich or Lean system causes the condition. Drive the vehicle at the speed of the complaint. Monitoring the Fuel Trim will help identify the problem.

- Lean - The Long Term Fuel Trim will be greater than 150. Refer to DTC P0171 "Diagnostic Aids." Testing and Inspection

- Rich - The Long Term Fuel Trim will be less than 115. Refer to DTC P0172 "Diagnostic Aids." Testing and Inspection

^ Check the fuel pressure while condition exists. Refer to "Table A-7B." Related Tests, Information and Procedures

Ignition System Checks

^ Check for the proper ignition voltage output using the spark tester J 26792 or equivalent.

^ Check the spark plugs for the following:

- Terminal screw - bent, loose (rotate and pull)

- Ceramic Insulator - cracks, tracking, deposits (red or black dust)

- Tip Insulator - cracks, tracking, deposits (oil, carbon, glazing, fuel additive), loose (rattles)

- Center electrode - loose (wiggles side to side)

- Platinum pads - missing, wear, gap size (too large or too small)
^ 5Check the ignition timing.

Additional Checks

^ Check the ECM/PCM grounds for being clean, tight, and in their proper locations. Refer to Starting and Charging / Power and Ground Distribution / Locations.

^ Check the generator output voltage.

^ Check the vacuum lines for kinks or leaks. Refer to the "Vehicle Emission Control Information" label.

^ Check Manifold Absolute Pressure (MAP) sensor scan tool parameter for being fixed, or slow response when throttle is snapped.

^ Check for an intermittent EGR problem.