Van shakes, makes knocking noise - 1993 GMC G2500
Hello. You will need to find out if your engine is misfiring due to an ignition part like plug wires (https://www.yourmechanic.com/services/ignition-cable-spark-plug-wires-replacement), plugs (https://www.yourmechanic.com/services/spark-plugs-replacement), or distributor parts like a cap and rotor (https://www.yourmechanic.com/services/distributor-rotor-and-cap-replacement) or the module. If all the tune-up maintenance...