Trouble Shooting: Surging
- Check EGR valve operation. See CHART C-7 (2.8L and 4.3L ) or CHART C-7A (2.5L) in GENERAL MOTORS COMPUTER COMMAND CONTROL article in COMPUTERIZED ENGINE CONTROL section.
- Check ignition timing. Check fuel filter for restrictions. Check fuel pressure. Check alternator output voltage. Repair if less than 9 volts or more than 16 volts.
- Remove and inspect oxygen sensor for silicon contamination from fuel, or improper use of RTV sealant. Sensor may have a White powdery coating, and will result in a high, but false, signal voltage (rich exhaust indication). Check ignition system.