If the timing in your 1996 Chevrolet Astro Van is off by a few degrees your van will start, and even run, but will be rough and tend to chug, ping or knock because of a lack of power to the engine. It can also cause your van to burn more fuel, have trouble starting or overheat. If the timing is off by more than a few degrees, your van will not start at all. Astro vans of this age tend to have worn timing chains and/or gears which will cause your timing to fluctuate and necessitate adjustment.
Start your vehicle and allow it to reach a normal operating temperature. Turn the air conditioner off.
Apply the parking brake and block the wheels so the van remains stationary. If you have an automatic transmission, put the van in Park, and if you have a manual transmission, put it in Neutral.
Remove the instrument panel support braces from each side of the engine cover, using a screwdriver. Loosen the upper retaining screws on the engine cover. These screws can only be loosened, and not removed, because they are captured in the brackets. Unlock the two latches on the bottom of the engine cover and remove it from the vehicle.
Bypass the electronic spark timing before checking the timing. Remove the single tan wire with a black stripe connected to the distributor. Unplug the connector, but do not unplug the 4-wire harness cover at the distributor.
Find the timing marks at the front of the engine. It is more difficult to see these components in an Astro Van because of the tight fit of components in the engine compartment. The crankshaft pulley or vibration damper has a notch in it and a small metal plate with notches and numbers is attached to the timing cover. Clean the plate with solvent, if necessary, so you can see the numbers. .
Use chalk to mark the notch or groove in the pulley or vibration damper. Highlight the notch or point on the timing plate that corresponds to the correct ignition timing specification. You will find this on the Emission Control Information label under the hood of the van.
Hook up an inductive pick-up timing light according to the manufacturer's directions. Make sure the timing light wires are not near the drivebelts or fan and then start the engine.
Allow the idle to stabilize and then point the timing light at the timing marks. Because of the tight fit of the components in the engine compartment of an Astro van you may need to push the radiator hose out of the way. Be aware of moving components, and keep both the timing light and yourself clear of them.
Notice the mark you made on the pulley/vibration damper. It should appear stationary. If it is aligned with the specified point on the timing plate, your timing is set correctly. If the marks are not aligned, you will need to adjust the timing.
Loosen the distributor hold-down bolt and turn the distributor slowly until the marks are aligned. Access to this bolt is limited and you may need a special distributor wrench to turn it.
Tighten the bolt. Recheck the timing. Turn off the engine and remove the timing light.
Reconnect the wire harness connector. Clear any trouble codes.
