Piston hitting plug?
 

I will just cut to the chase... Somehow, cylinder 4 spark plug keeps loosing its gap. Pull it out, gap it, and sometimes it will run great for a week, somtimes an hour. I looked into the sube and the piston is not cracked or anything like that, I checked timing last night, (just cam) and it was dead nuts. I put a 2nd spark plug washer on it last night, and took it for a drive, and same thing. I am stumped. Thinking about another washer tonight as a temp solution, but what could this be?? I have had the car, not even a month now, and it has done this since day one of getting it. Maybe head milled wrong? Try a thicker head gasket?

I saw on here that people have had this problem on cylinder 3, but they are WAY more smashed then mine, mine is just barley tapped shut. My first EVO headache! haha

Man, talking to guy here..he thinks it is carbon build up, he said clearances so close on this engine, and carbon can be as strong as a rock, and over time, just gets taller and taller. That makes lots of sense to me, and it is very dirty looking in it. But now looking into a solution while keeping the head on. hmm
-Russ

Hey Russ, do you have a borescope to look through the spark plug hole? Do you have the right spark plugs? The reason I ask is because your valves should be lower and should contact your piston before your spark plugs. I can measure when I get home.https://cimg5.ibsrv.net/gimg/www.evo...26dcf9e19a.jpg

Thanks everyone for the fast responses. The spark plugs I am currently using are NGK BR8ES and installed by a local tuner, They are shorter then the factory ones that where in the car. So I just ordered some washers to try to raise it up, but looking at your picture, that is very confusing as how this could happen?? It does look like lifters would get hit first. Hmm, Maybe more reason to think carbon build up? I took them out, and number 1 also lost its gap this time, WTF???? I am thinking this might be why I got such a good deal on this car, as they could not figure it out. The PO claimed it was sitting for a year, but I found documents from last oil change, looks like closer to 2 years vs 1. Not sure if that effect anything or not.

I might have access to a scope to try later this weekend, but as of right now, I have just looked in the holes with a flashlight, at both piston all the way down, and all the way up and do not see any extra stuff in it, going to attempt to put a magnet in there to move around and see if any metal pieces in there. They pistons are very carbon/dirty, no doubt about that, but never thought carbon got that hard? I have also read if timing is off, the denotation can bend them? but when they are working, it runs amazing, lots of torque even without boost, so I do not thing timing is an issue. It does make loud mechanical noises at high RPM, more so then I think it should make, but not 100% sure as this is my first Evo, so not much to compare it to.

Sounds like a ghetto, half assed fix trying this washer plan, but as of right now, I have no other ideas,

above you mentioned I have never heard any good experiences with it, but willing to try it.

There is about 7.5 mm clearance from spark plug to head surface. Piston can't touch spark plug without crushing head. Make sure you have the correct spark plug.
I can't imagine 7mm thick of carbon buildup. Lol

Ohh sorry, measure it.

https://cimg9.ibsrv.net/gimg/www.evo...fcb13179d1.jpg

Those are short. Something else is causing the problem. The intake valves and cylinder had would hit first by piston before it gets to your plug. How was your old plug before it was replaced? Maybe a piece broke off and is still bouncing around inside?

It's not timing problem because that only controls your valves. Same with lifters. Good luck with magnet. That reminds me about ice fishing. :lol:
I guess detonation could bend them, but it will do other more serious damage, so I think it's unlikely.

Here are a few more pictures. Maybe you can find other potential causes? (Ignore my trash bag:lol:)https://cimg6.ibsrv.net/gimg/www.evo...b6408c8412.jpg
https://cimg8.ibsrv.net/gimg/www.evo...a3155ca6a3.jpg

Detonation will close the spark plug gap. You may have a bad fuel injector.

What about being tuned on 93, and driving on 91 as no 93 in Vegas? I get some DEEP backfires at times while decelerating at times. Injectors are factory, non upgraded at all.

Just did the magnet test, nothing in there. But, it gave me a chance to really feel the pistons, and they are very carbon, feels like asphalt in there, atleast number 1 and 4, the others are smoother, but still like sand paper. This is soo odd haha. I am very fast at pulling the plugs though now, so that is a plus. I am not worried that I bend the gap back and forth so much it is gonna break off eventually. Pulling the whole head really does not look too hard on this car, but currently my only car, so it would be a pain finding time to do it.

letsgetthisdone is close to you if you need a pro.

I am being a bit naive, but I am in hopes right now that these washers that are getting delivered here soon will fix all haha Someone elsewhere said WD40 will clean it up. He said get liquid type, not the spray, and pour it in there, let it set for like 2 days, after 2 days leave plugs out and crank the engine a bit, change the oil, put it together and start her up. It will clean up the carbon on the pistons, and its great for teh rings as well.. This sounds absolutely terrifying to me! I do not think I will try it, but interesting idea for sure.

What do you mean by "deep"?