Surges and/or Chuggles

Definition: Engine power variation under steady throttle or cruise. Feels like the car speeds up and slows down with no change in the acceleration pedal.


PRELIMINARY CHECKS

^ Perform the careful visual checks as described at start of "Symptoms,".

^ Be sure driver understands transmission operation, and air conditioning compressor operation as explained in the owner's manual.


SENSORS

^ CHECK: Heated oxygen sensor (HO2S). The HO2S should respond quickly to different throttle position, if it does not, check the HO2S for silicon or other contaminations 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 (rich heated HO2S signal indication). The engine control module 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

^ NOTICE: To determine if the condition is caused by a rich or lean system, the car should be driven at the speed of the complaint. Monitoring block learn will help identify a problem.

Lean - Block learn above 142. Refer to "Diagnostic Aids" for diagnostic trouble code 44.

Rich - L.T. Fuel Trim above 118. Refer to "Diagnostic Aids" for diagnostic trouble code 45.

^ CHECK: Fuel pressure while condition exists. Use CHART A-7.

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


IGNITION SYSTEM

^ CHECK: For proper ignition voltage output using spark tester (ST-125) J26792 or equivalent.

^ CHECK: 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 electronic ignition and spark plug wires.

^ CHECK: Ignition timing. Using "Scan tool".


ADDITIONAL CHECKS

^ CHECK: Engine control module grounds for being clean, tight and in their proper lo-cation.

^ CHECK: Vacuum lines for kinks or leaks.

^ CHECK: Exhaust gas recirculation - There should be no exhaust gas recirculation at idle. Refer to CHART C-7.

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