Set the timing on a 4.3 astro van with a timing light

SOURCE: my van

the timing isn't something you set it say this on my 97 astro

SOURCE: 4L60E Slips after about 1/4 mile. 2000 Chevy Astro Van Transmissi

sadly, it sounds like a bad torque converter.

SOURCE: 2001 astro chevy van 4.3 engines need to set the timing

The distributor in that engine can only be installed in one position. The hold down is built onto the distributor meaning when it is installed and the engine runs the computer is responsible for the timing. The distributor will move a little but won't correct major timing errors.

SOURCE: Timing on an astro van

No it can not it is run by the cars computer. If the distrubitor cap is on wrong than that can cause multiple misfire

SOURCE: My 1995 chevy astro van shakes every time i break

you either have bad brake pads or the bolts are loose that hold the front steering suspension on.