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
^ Perform the careful visual checks as described in Diagnostic Notes. Refer to Diagnosis By Symptom / Preliminary.

^ Be sure driver understands transmission [1][2]torque converter clutch and A/C compressor operation as explained in the owners manual.

ADDITIONAL CHECKS
^ 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 volts or more than 16 volts.
^ Speedometer reading with the speed on a Tech 1 scan tool are equal.
^ Service Bulletins for updates.

SENSORS
^ Check Heated Oxygen Sensor (HO2S). 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 Powertrain Control Module (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
^ Check for proper ignition voltage output using spark tester (ST-125) J 26792 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 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. Use Diagnostic Aids in text of Diagnostic Trouble Code (DTC) 44. Refer to Diagnostic Charts / Diagnostic Trouble Code Charts / Code 44 Heated Oxygen Sensor (HO2S) Circuit (Lean Exhaust) Powertrain Controls - ECM/PCM

Rich - Long term fuel trim below 110. Use Diagnostic Aids in text of Diagnostic Trouble Code (DTC) 45. Refer to Diagnostic Charts / Diagnostic Trouble Code Charts / Code 45 Heated Oxygen Sensor (HO2S) Circuit (Rich Exhaust). Powertrain Controls - ECM/PCM

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