The 4.3-liter engine primarily powered Chevrolet and GMC pickup trucks in 1992. Proper ignition timing plays a crucial role in engine performance. If the timing is off, the engine may overheat, lose power, stall, backfire, stop running or fail to start. Permanent engine damage can occur if the pistons strike the valves repeatedly. If the timing belt or chain on the vehicle is functioning correctly, you must simply reset the timing on the vehicle to restore the engine's performance. Set the ignition timing under the hood near the crankshaft pulley.
Look into the engine block for the metal timing scale, a component measuring 4 inches long sitting just above the crankshaft pulley (the bottom pulley). You will probably need to remove the road grime to make the numbers legible. A can of aerosol brake cleaner or penetrating oil and a shop towel will take care of the problem.
Locate the dampener pulley positioned directly behind the crankshaft pulley. You will find a deep groove cut into the dampener pulley. Highlight the groove with your chalk or paint marker to make it easy to see in future steps.
Move to the passenger-side firewall, and find the bypass connectors behind the relay panel cover. Remove the three plastic nuts that hold the cover in place. The bypass connector itself is a tan wire with a black stripe that divides into two sections. Unplug the connector to put the vehicle's computer into "base timing" mode and allow it to receive an accurate signal from the distributor.
Find the distributor at the rear of the engine. Loosen the lock-down bolt underneath the distributor using a distributor wrench. Loosen it just enough that you can turn it.
Connect your timing light to the vehicle's battery. As with battery cables, the red clip connects to the positive side, and the black to the negative. The light's inductive pickup wire connects to the outside of the No. 1 spark plug wire - -the front one on the driver's side. Try to get as close to the base of the wire as you can, which will produce the most accurate reading.
Engage your emergency brake. Put your transmission in neutral if you have a manual, or park if you have an automatic. Start your vehicle, and allow it to warm up for about five minutes while idling.
Point the timing light to the timing scale with the truck idling. The light will flash and illuminate the numbers on the scale and the dampener groove you highlighted earlier. This flash represents the exact time that spark plug wire received its signal from the distributor.
Adjust the distributor gently by turning it until the groove on the dampener pulley aligns with "0" on the scale.
Retighten the distributor, and recheck the timing. If it is still correct, turn the vehicle off and disconnect the timing light. Reconnect the bypass connector, and attach the cover.
