Surges/Chuggles

DEFINITION
Engine power variation under throttle or cruise. Feels like the vehicle speeds up and slows down with no change in accelerator pedal position.

PRELIMINARY INSPECTION
^ Perform the careful "Visual And Physical Checks" in Preliminary Checks. Testing and Inspection

SENSORS
^ CHECK: Oxygen sensor (02S). The 02S should respond quickly to different throttle positions. If it does not, check the sensor for silicone 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 exhaust indication). The ECM 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

NOTE: 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 O2S voltage will help identify a problem.

Lean - Refer to "Diagnostic Aids" under Diagnostic Trouble Code 25. DTC 25
Rich - Refer to "Diagnostic Aids" under Diagnostic Trouble Code 26. DTC 26

^ CHECK: Fuel filter. Replace if dirty or plugged.
^ CHECK: Fuel pressure while condition exists. Refer to Fuel System Pressure Test.

IGNITION SYSTEM
^ CHECK: For proper ignition voltage output using 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 distributor cap, rotor and spark plug wires.
^ CHECK: Ignition timing. Refer to Ignition Timing Adjustment. Ignition Timing

ADDITIONAL CHECKS
^ CHECK: ECM grounds for being clean, tight and in their proper location.
^ CHECK: Vacuum hoses for kinks or leaks.
^ CHECK: Generator output voltage. Repair if less than 12 or more than 16 volts.
^ CHECK: EGR - There should be no EGR at idle (if equipped). Refer to Exhaust Gas Recirculation System Check. Testing and Inspection