Engine Knock - 92 Mistubishi Expo SP - 196k

Hi Group - 1’st Post… 1992 Mitsubishi Expo SP w/ 2.4l 4cyl engine. 196k - Amazing reliability. The auto has developed a recent (last 1500 miles) engine knock problem. Thought fuel issue - changed fuel, additive to tank etc…but no change. Thought tune-up (cap, rotor, plugs, wires). Did not change. Problem is mostly when engine is warm, and only under load (steep hill when on the highway). I’ve been taking off cruise and letting off on the accelerator to reduce the knock sound. Startup, idle and running around town seem normal - in fact it’s running great since the tune-up!

Sugggestions? Help please.


Check out the Exhaust Gas Recirculation system. Make sure that the EGR vacuum plumbing is intact, connected, and not leaking. Make sure the diaphragm of the EGR valve is not leaking. Check the valve to see if it is flowing exhaust by lifting the valve using a vacuum source at idle and seeing if the engine dies. Since this is a OBDI system the computer probably will not set a code for inadequate EGR flow but you might check for DTC codes. Also make sure that the base ignition timing is correct. If this engine has a knock sensor, there may be a problem with that.

Let us know what cures this problem.