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 acceleration pedal.

PRELIMINARY CHECKS
- Perform the careful visual / physical checks as described in Preliminary Checks.
- Be sure driver understands transmission [1][2]torque converter clutch, and A/C compressor operation as explained in the owners manual.

SENSORS
Check the Heated Oxygen Sensor (HO2S). The heated oxygen sensor should respond quickly to different throttle positions; if it does not, check the heated oxygen sensor for silicon or other contaminants from fuel or use of improper RTV sealant. The sensor may have a white, powdery coating and 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.

FUEL SYSTEM

NOTICE: 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 L.T. fuel trim and S.T. fuel trim will help identify a problem. Refer to Scan Tool Diagnostics / Typical Tech 1 Scan Tool Data Definitions for an explanation of L.T. fuel trim and S.T. fuel trim. A poor PCM ground at the ignition control module mounting bracket may cause the S.T. fuel trim to read about 159.


- Check the fuel pressure while condition exists. Use Chart A-7. Testing and Inspection
- Check the in-line fuel filter. Replace if restricted, dirty or plugged.

IGNITION SYSTEM
- Check for adequate ignition voltage output using spark tester J 26792 (ST 125) or equivalent. Test one spark plug wire at a time.
- 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 condition of spark plug wires.

ADDITIONAL CHECKS
- Check PCM grounds for being clean, tight and in their proper location.
- Check Vacuum lines for kinks or leaks.
- Check the Generator output voltage. Repair if less than 9 or more than 17 volts.
- Check the speedometer reading and the speed displayed on a Tech 1 should be equal.