The 4.3 liter V-6 engine used in GM trucks and vans, beginning in 1985, is based on the Chevy 350 small-block V-8. Beginning in 1988, this engine featured “Vortec” cylinder heads that created a swirling air/fuel mixture in the cylinder for improved combustion efficiency. Setting the base ignition timing in this engine is critical to the engine’s performance, because on-board computer control of ignition timing during operation assumes base timing is accurate. The average home mechanic can complete this procedure in a few minutes.
Start and warm the engine until the thermostat opens. The upper radiator hose will get hot when the thermostat opens and the coolant is circulating freely through the engine. This ensures normal operating temp has been reached and the on-board computer is operating in closed loop. Stop the engine.