Surges/Chuggles

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

PRELIMINARY CHECKS
Perform the careful visual/physical check as described in Preliminary Checks.
Be sure driver understands A/C compressor operation as explained in the owner's manual.

SENSORS
Check:
Heated oxygen sensor(s). The Heated Oxygen Sensor(s) (HO2S) should respond quickly to different throttle positions, if they do not, check the HO2S for silicon or other contaminates 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 HO2S signal). The Powertrain Control Module (PCM) will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.

FUEL SYSTEM

NOTE: To determine if the condition is caused by a rich or lean H02S signal, the vehicle should be driven at the speed of the complaint. Monitoring long term fuel trim will help identify a problem.
Lean - Long term fuel trim near 160. Refer to "Diagnostic Aids" in DTC 42 or 44.
Rich - Long term fuel trim near 115. Refer to "Diagnostic Aids" in DTC 43 or 45.
Refer to "Diagnostic Aids" in DTC 46. Testing and Inspection

Check:
Fuel pressure while condition exists, use Chart A-7. Testing and Inspection
In-line fuel filter. Replace if dirty or plugged.
CHECK: A faulty heated oxygen sensor heater circuit could cause a rough idle condition. Refer to Chart C-1D for diagnosis of the heater circuit. Testing and Inspection

IGNITION SYSTEM
Check:
For proper ignition voltage output using spark tester (ST 125) J 26792 or equivalent.
Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

ADDITIONAL CHECKS
Check:
PCM grounds for being clean, tight and in their proper location.
Vacuum lines for kinks or leaks.
Generator output voltage. Repair if less than 9 or more than 17.3 volts.
EGR operation, use Chart C-7. Testing and Inspection
Speedometer reading and the speed displayed on a Tech 1 should be equal.