Mitsubishi Repair: 1996 Eclipse 2.0 eengine loud knocking, valve lifters, oil residue

Question
I have a 1996 Eclipse 140,000 miles. It just recently developed a loud knocking coming from the top of the engine, almost sounds like a valve possibly hitting a piston. It was running fine untill this developed. do you have any idea what this could be?

Answer
Greg,
This could be sticky valve lifters.  Over time, they can get clogged with oil residue and fail to lubricate properly.  This can cause a clacking or knocking noise.  If the noise is loud and persistent enough, it can cause your knock sensor to retard the timing and decrease overall engine performance.  The best thing to do is to pull all 16 lifters and give them a good cleaning.  Beyond that, you may want to have your timing belt inspected.  If it's been more than 60,000 miles since last you replaced it, it's possible the belt could have slipped a tooth and is throwing off your timing.  The last thing you want is your timing belt to break while you'll driving.
Good luck!