Surges/Chuggles
DEFINITIONEngine 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 visual/physical checks as described at start of Preliminary Checks.
^ Make sure the driver is using the correct starting procedure.
SENSOR CHECKS
Oxygen Sensor (O2S). The O2S should respond rapidly to the varying quantities of oxygen in the exhaust system. After the O2S has reached operating temperature, the voltage should change quickly, and can go as high as 1 volt and as low as 0.1 volt in less than a second. If this response time is slow or voltage is at a steady level, the O2S should be checked for silicon, glycol or other contamination The O2S may have a white powdery coating (silicon contamination) or a green coating (glycol contamination) that would result in a false signal voltage to the Powertrain Control Module (PCM), and may lead to a driveability complaint.
IGNITION SYSTEM CHECK
^ For adequate ignition voltage output using spark tester J 26792 (ST 125) or equivalent.
^ Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Spray spark plug cables with a mist of water and check for shorts. Repair or replace as necessary.
FUEL SYSTEM CHECK
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 Long Term (L.T.) fuel trim will help identify a problem.
Lean - L.T. Fuel Trim near 198. Refer to "Diagnostic Aids" in the text of Diagnostic Chart 44. Refer to Computers and Control Systems / Testing and Inspection / Procedures / Diagnostic Charts / Diagnostic Trouble Code Charts. Testing and Inspection
Rich - L.T. Fuel Trim near 58. Refer to "Diagnostic Aids" in the text of Diagnostic Chart 45. Refer to Computers and Control Systems / Testing and Inspection / Procedures / Diagnostic Charts / Diagnostic Trouble Code Charts. Testing and Inspection
^ Fuel pressure while condition exists. Use Chart A-7. Refer to Computers and Control Systems / Testing and Inspection / Procedures / Diagnostic Charts / A Charts. Testing and Inspection
^ In-line fuel filter. Replace if restricted, dirty or plugged.
^ For plugged injectors per injector balance test.
^ For Contaminated Fuel.
ADDITIONAL CHECKS
^ Vacuum lines for kinks or leaks.
^ Generator output voltage. Repair if less than 9 or more than 16 volts.
^ PCM grounds for being clean, tight and in their proper location.