Surges/Chuggles

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

PRELIMINARY CHECKS
1. Perform careful visual and physical checks as described in preliminary checks. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnosis by Symptom / Preliminary Checks. Testing and Inspection
2. Be sure driver understands transmission [1][2]torque converter clutch and A/C compressor operation as explained in the owner's manual.

ADDITIONAL CHECKS
1. Check the Powertrain Control Module (PCM) grounds for being clean, tight and in their proper location.
2. Check vacuum lines for kinks or leaks.
3. Check generator output voltage. Repair if less than 9 volts or more than 16 volts.
4. Check speedometer display with the reading on a Tech 1 scan tool are equal.
5. Check Service Bulletins for updates.

SENSORS
Check the 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 improper use of RTV sealant. The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Also, watch for green (glycol) contamination or cracking.

IGNITION SYSTEM
1. Check for proper ignition voltage output using spark tester (ST-125) J 26792 or equivalent.
2. Check the 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 spark plug wires.

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 long term and short term fuel trim will help identify a problem.
Lean - Long term fuel trim above 150. Refer to "Diagnostic Aids" in Diagnostic Trouble Code (DTC) 44. Powertrain Controls - ECM/PCM
Rich - Long term fuel trim below 110. Refer to "Diagnostic Aids" in DTC 45. Powertrain Controls - ECM/PCM

1. Perform the "Injector Coil / Balance Test." Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart C2-A. Chart C-2A Fuel Injector Balance Test
2. Check fuel pressure while condition exists. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart A-7. Related Tests, Information and Procedures
3. Check the in-line fuel filter. Replace if dirty or plugged.