+10000000

 

Ok Mitsu just called back. Car's all fixed. It was just a fouled spark plug... again... I didn't see anywhere in the owners manual stating oil change and #4 spark plug change every 3k miles...

So I asked the rep to reiterate what he said this morning. Short trips cause fouled spark plugs. Short trips or turning the car on and then off right away.

Me:
Did you do a compression test?

The Rep:
No this was a carbon fouled spark plug. Blow by would result in a wets plug. There were no stored codes and no reason to investigate further.

Me:
If this happens again in another month then this warrants further investigation beyond just a spark plug.

The Rep:
Yes I agree with that.

 

I would bring in a video of a video borescope showing part of the piston missing.

Pay for a compression check and leakdown on your own dime from the dealer.

 

That is a very good idea. I got a borescope originally @ AMS and it showed nothing upon the first instance of this issue. I am sure after this issue has reoccurred multiple times that it has to be a mess in #4 and #1 by now.

 

Got my car back with my fancy new #4 spark plug yesterday and I could still get the thing to buck. It hesitates upon acceleration at times. This morning I got on the highway and shortly thereafter the SES light came on.... yesssss! Back to Mitsu I go. Could just be the #1 spark plug now since I have had the piston chipping issue on that cylinder as well. As always I will keep the thread updated.

 

Ok so I went to pick up my car for the SES light part 2. They claim the spark plugs all had some carbon build up. So they replaced them all. Also a boroscope was done on each cylinder which they discovered carbon build up in the cylinders as well. They were able to clean most of it out. This should not happen again.

Me:
I asked so if and when this does happen again what are the next steps to figuring out this problem.

Service Rep:
Then at that point we will have to take the head off and see whats going on in there.

Bingo. IMHO this should have been done immediately but I can live with that. So I'm off again in my Evo 10 with all fresh plugs. My bet is... 1.5k-2k miles before Im back in with this problem.

 

I doubt they actually put a camera in the cylinders.

 

#4 Piston

#2 Piston

 

Number 4 is the culprit but when the ring broke it got sucked into the intake manifold and ejected back into #2 it appears.

I have seen others where the same thing happens but the ring gets sucked into #1 and makes the same staple marks.

We have the first of our 4b11 Aluminum rod engines complete +.20 over CP pistons on A1000 rods, Cosworth bearings with the moly rings set for the proper clearances for high performance engines. The part that the factory failed miserably at setting up correctly.

We will be adding them to our site shortly. Anyone interested can send us a PM.

 

Would U hazardous a guess at to why Mitsu made these clearances so tight? Just an outright error or was it for pollution control or minimizing oil dilution or both?

Later, Ken

 

Just to clear this up, I am sure I missed this somewhere.

1. This can happen and is happening on stock turbo cars.
2. Usually triggered by large amounts of boost(+30lbs), either boost spike or MBC.
3. This condition doesn't occur at 28psi or less

Are these points correct?

 

Nothing in life lives by rules. However higher boost coupled with the heat of expanding pistons from spirited driving is enough to collide the ring ends together.

I cannot speculate why Mitsu made the end gaps .007

Either they shipped wrong specs from the factory at assembly or they just never set the ring end gaps at all. Just took them out of the box and threw them in.

I cannot see any engine mfr making motors for this long screwing up like this, yet here we are. Anyone know where these engines were assembled?

 

just to clarify...

my car closed the gap when all i had was a mbc and a tune @24psi.

i took it to the dealership and they told me that the spark plug was deformed from manufacture. I asked specifically if the spark plug was hit by something and they told me no. everything was good. By the time i realized what was going on, it was too late.

 

It seems the majority of folks I have seen have had mild bolt-ons running close to stock boost. Some completely stock. Mine was running @ 22psi.

 

Thanks for posting the pics

I am sure my #4 is this bad or worse. I've had 3 occurrences of chipping pistons. 2 bent the #4 spark plug ground strap and 1 bent the #1 ground strap. Who know's if this means what TTP described with the pieces from the #4 piston ending up in cylinder #1 or not Won't know until tear down.