i have a 1992 gmc full size van when it cold it will run great but when it warms up it will skipping
An engine will run a little richer until it warms. The spark plugs may not be able to fire a leaner mixture when it’s warm. Put in fresh spark plugs. Pull a spark plug wire and test for spark strength. If it has a weak spark, change the spark plug wires, rotor and distributor cap (if it has them).