Surges Or CHUGGLES
Engine power may vary at cruising speed, or under steady throttle without moving the accelerator pedal. Use a scan tester to verify Vehicle Speed Sensor (VSS) signal matches vehicle speed. See VEHICLE SPEED SENSOR (VSS) under ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS article in this section. Check the following items:
- Ensure EGR system is okay at idle. See I - SYS/COMP TESTS article in this section.
- Ensure ignition system output is correct.
- Check fuel filter for dirt or restrictions.
- Ensure fuel pressure is correct.
- Check vacuum hoses.
- Check ECM ground contact on engine.
- Ensure alternator output voltage is 9-16 volts.
- Ensure TCC operation is correct. See I - SYS/COMP TESTS article in this section.
- Check O2 sensor for silicone contamination from fuel or incorrect silicone sealant. Sensor may have a White powdery coating, and signal a false rich mixture signal voltage. This signal will cause ECM to reduce fuel, causing lean mixture and driveability problems.
- Remove spark plugs and check for cracks, wear, incorrect gap, or heavy deposits.