How to Adjust the Timing on My 1997 GMC Yukonby Lee Sallings
Adjusting the ignition timing on your 1997 GMC Yukon is a normal part of a yearly tuneup. Wear on the distributor drive gears, and timing chain stretch, cause the ignition timing to change. Inaccurate ignition timing caused by this wear will result in a loss of power and fuel economy that can be compensated for by adjusting the timing. Common automotive tools and equipment are required for this procedure and are available at most auto parts stores.
Start your 1997 GMC Yukon and allow the engine to run till operating temp is indicated on the temperature gauge on the dash. Turn off the engine and leave the ignition key in the off position.
Disconnect the timing connector located on the main wiring harness. The main wiring harness in the 1997 Yukon runs behind the engine, along the firewall, in the rear of the engine compartment. The timing connector is a small single wire connector attached to a tan wire with a black stripe on it.
Attach the timing light to the battery terminals. Clip the red power wire to the positive battery terminal and the black ground wire to the ground terminal on the battery. Open the spark plug wire lead on the timing light and clip it around the front spark plug wire on the driver's side of the engine. Start the engine.
Aim the light at the Yukon's timing marks located above the crankshaft pulley on the front of the engine. The strobe light effect of the timing light will make the crankshaft pulley appear to stop spinning. Note the position of the groove on the back of the pulley in relation to the marks on the timing tab above the pulley.
Loosen the bolt that secures the distributor in the engine, located at the base of the distributor, using a 9/16-inch distributor wrench. Rotate the distributor with you hand while watch in the timing marks on the front of the engine, until the mark on the pulley aligns with the 10-degrees mark on the timing tab. Tighten the distributor bolt.
Turn off engine and disconnect the negative battery cable from the battery using an 8-mm wrench. Reconnect the timing connector and remove timing light from the engine compartment. Reconnect battery cable to the battery after 5 minutes and test drive the Yukon.
- Wear safety glasses and work gloves when working around a running engine to prevent serious injuries.