Wnbevo

Hi! My brother bought an EVO about an month ago and the engine had been rebuilt with some better pistons 12K miles ago. We checked the compression back then and it were 175 PSI across the board.

Couple weeks ago he were just casually driving to home from work and when he stopped to a stop light, the car started to run like a Subaru and lost Idle.

We tried swapping the plug wires, plugs, coilpacks and injectors around but the problem stayed in the same cylinder #2 every time, so we then decided to do a compression test and compression in the cylinder #2 were as low as 95psi.

So that happened all of a sudden and the engine doesn't make any weird noises. Just sounds like the second cylinder isn't firing but doesn't sound like something is mecanically wrong.

Hope you understand what im saying because english is my third language lol.

barneyb

Time for a leak down test to see where the air is going.

4b11slayer

^^ agreed.

Cylinder leak down test is in order.

Your not complaining of smoke so i doubt its piston related. I would say a burnt or chilled exhaust valve.

Do leakdown and report back.

Note: the cylinder that is being leak down tested MUST be at Compression Top Dead Center. If its on exhaust stroke it will be 100% leak.

Evolved25

I would say possible tuliped valve or piston ring at least you know it's something mechanical which narrows it down a lot.

RightSaid fred

Photos of sparkplugs?

Wnbevo

Don't​ have pictures but the spark plugs were fine. We just changed them few weeks before this happened.

He told me that he's actually gonna get the car towed to a shop and let them fix it for him.
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He's not doing a leak down test but thanks for your help! I'll report back when I know what the issue really is, although it sounds like a burnt exhaust valve when you really think it.

Wnbevo

It's been a while. The car were sitting at my brothers apartment so he got it trailered to my place about an week ago, and after the sitting, the car is running on all four again so probably had stuck rings.. I re-checked the compression and now the compressions are:

1. 200psi
2. 180psi
3. 180psi
4. 200psi

Sounds healthy now but smokes a bit at high revs, and as soon as it starts to warm up, it starts to misfire at idle. The car isn't "on the road" now because he wants to fix a few minor faults so leak down test isn't doable.

The misfire isn't consistant, and by that I mean that it isn't happening for example at every 5 seconds.

I'm guessing that maybe the HG is leaking between the 2nd and 3rd cylinders now because the compression is down in those cylinders.. That could explain the misfire too.

I already tried capping the spark plugs but that didn't help, and I looked for vacuum leaks but wasn't able to find any.

One thing I also noticed that the turbo has too tiny comp. wheel for the housing, and it also has axial shaft play maybe 1mm or so, which doesn't sound good to me.

Wnbevo

UPDATE:

I've been dialing up few minor things with the car and the misfire has gotten worse. Haven't driven the car now but it misfires now on part throttle too. I know it could be as simple as spark plug wires so we need to try with new ones.

I just flushed the coolant system and after bleeding it I decided to do a quick compression test again. This time the results were; 1. 190psi, 2. 160psi, 3. 170psi and last but not least the fourth had 180psi.

It runs great (if you forget the misfire for a second) and smokes less than before. There also were zero oil in the coolant and it didn't make any bubbles after I was done with bleeding the coolant system.

RightSaid fred

Still waiting for photos of plugs?