I did a compression test and I got 120, 115, 115, 120.
It's good that it's even across, but it's low.
What are your thoughts, what would be the fix. Rebuild the head?

Car:
Evo 9 with 135k miles. All 100% stock except clutch.
Purchased it a few months ago from original owner.

Test:
Hot engine, good battery, cheap gauge,
all 4 spark plugs out, and both camshaft sensors unplugged.
I than added a cap of oil, and gained 5psi across.

Goal:
Add a test pipe, intake, and a conservative tune.

 

I think your ok if I recall I thought evo 9's tend to have slightly lower compression #'s, yours are all close to one another which is good. As far as the low #'s maybe it has to do with the 135k miles.

 

What kind of tester did you use? Don't look at the numbers being low. Right now they are within tolerance even with adding oil and only gaining 5psi. Motor sounds healthy to me. Do a leak down test as well.

 

If it doesn't blow smoke and still kicks butt just drive it like you stoll it

 

The numbers aren't far apart from each other, I'd be concerned if it was 140psi, 115psi, 135psi, 130psi - but just for a peace of mind I'd preform a leak down test. I feel a leak down test will provide you with better results on your engine state of health.

 

How was the condition of the battery? Also besides a hot engine, was the throttle wot? But like what others stated. Your numbers are pretty good not way off from one another. Your motor should be good.

 

Its fine. All the numbers are close together. I believe the minimum on an IX is something like 96 psi.

 

That car is fine I wouldnt touch it

 

IX's do have lower numbers than VIII's do. Can't remember where I read that here on the forum but there is a thread dedicated to it. I had the same numbers on mine last time that I checked and this is completely normal.

 

Just do a rebuild, get it over with. Do it right and hone the block. After an engine build it should be 165 across the board.

 

Sorry but disagree its within +/-5 of other cylinders and will be fine for plenty of miles. Do agree that getting a leakdown done would give additional information. Sounds like a motor that has a lot of miles but still good for some more. You could start saving money/getting parts for a rebuild down the road but your not in any real danger. If you had something like 120,115,101,115 then you would have a issue.

 

The spec for a IX is minimum of 92psi with a maximum difference between cylinders of 14psi



You're well within spec

 

It says the standard value is 145 PSI....if it's 92 it's toast.
You want it as good as possible which means close to 145.


Have you checked the cam timing?


You haven't said what the problem was for you to check the compression in the first place.


Looking at the sparkplugs usually tells you more than what the compression tester does.

 

How are you doing the test/cranking of the motor ? Are you cranking till the PSI stops climbing, cranking a X number of rotations, cranking X number of seconds etc... ?

 

are the cams stock?