Usually an indicator of worn rings when it's uniform like that. Looks like rebuild time.

 

I forgot to add that it was just rebuilt 1,600 miles ago!

 

Timing Off?

 

Would a cel code be thrown if it was off? Because I have no codes.

 

A shop did it, but it is over their "30 day warranty" period. And yes it is stock cams.

 

can they tell you what the piston to bore clearances were when the engine was assembled? Ring gap? What type of rings they used and pistons? If your using oil and the compression is as low as it is, the assembly clearances could be excessive or the rings never seated properly.

Do you have a turbo/vacuum gauge? What is the idle vacuum?

 

Your first mistake was probably going to a shop that only warranties for 30 days.

I bet they just dropped some stock sized pistons into your block without honing the bores. Since it's older they are probably a little worn. They should have honed and gone with slightly larger pistons.

On a fresh rebuild you should have 150+ PSI across the board and less than 5% leakdown.

90 psi isn't far off from what I would expect from a motor with a ringland issue.

 

...

90 psi isn't far off from what I would expect from a motor with a ringland issue.

One of my cracked ringlands did hit 90psi...

 

I didn't choose the shop. My aftermarket warranty chose the shop. And my idle vacuum is about 10psi!

 

WAY too low, normal idle vac. with a healthy stock rebuild and stock cams should be 20-21, my guess is all the piston clearances are excessive. If the shop is telling you they won't work with you because your past the 30 day's I'd probably not even go back there. Take it to a well known, shop in your area that works on EJ's a lot.

 

Was the car tuned? You originally bought it and it blew up because it wasn't tuned and now its happening again on the rebuilt motor? One of your posts state that you were getting a tune but you claimed to drive it hard before that?

 

The car is tuned on a cobb OTS stage 2 map. And everything I have heard and read says that 10 psi is normal for an sti engine, 10psi = 20-21Hg so I think that is was you may be referring to.

 

Oh LOL..I though YOU meant it was only 10 Hg. Is it a steady needle or bouncing? Are you using oil? And did the shop have an explanation for why the compression readings were so low?

 

Mabye they didnt rebuild it and threw in another used motor. Its been know to happen by those shady aftermarket warranty companies.

 

The needle stays pretty still for the most part, and I don't really have any oil consumption. I just think it is very strange that they are all uniformally low.

 

What did the shop say about the low readings??? Either the compression ring clearance is too much or the intake and exhaust valve timing are staying open too long. If your not using oil the oil control rings sound like they are working OK for now...but then again you havent gone 3000 miles yet. Its also possible that depending on the type of rings they used they havent completely seated yet and your compression readings will be higher after some more miles. Not much else it could be unless the head gaskets werent torqued properly, but you'd probably have much more noticeable driveability problems in that scenario.

 

They didn't say anything about the low numbers (weird, I know). They said something along the lines of them thinking that the rings they used were nickel coated or something and it could take a while to wear them in. But I don't know. It just all seems strange to me.

 

Find out the brand and series of the rings they used and post it up on here. The fact they mentioned a certain style of rings could mean that they need more time to fully seat. Your driving style could be delaying that if your not getting enough pressure/loan on the rings for the material they used. Some rings ARE NOT compatible with Synthetic oil either, it's too slick to allow for the rings to seat and conventional oil has to be used for the intitial break in for a good 2000 miles for example....and THEN the switch to synthetic is OK. If they used rings like that and filled the crank with synthetic your rings havent seated...and they might not now even if you switch to conventional. Ask them the brand of rings they used and the composition so we can eliminate this possibility.

 

How is the car running? What caused you to do the compression test. I have seen faulty test readings from a cheapo compression gauge( brand new out of the box) and especially since they are all the same this could be the case. Compression this low and you will notice engine problems so now I question the test results especially if the car is running fine. You never mentioned any drivability problems?

 

I will try to find out what rings were used. The car seems to be running very well to me. And what caused me to do a compression test was a very slight steam from the oil filler cap which turned out to just be a tiny bit of hot oil vapor. I'm pretty sure he said he used either a Snap-On or Mac gauge. And no I haven't really seen any drivability issues. Anything in specific you would like me to try or look out for?

Also, shouldn't my compression numbers be higher since I only have very slight leakage, or am I wrong in assuming that?

 

Who did the compression test? Did they have the throttle WOT when cranking? All these little things can cause these problems. Low compression in a cylinder usually causes misfires and you said no CEL.

 

A local shop did the test. And do you think that if maybe he didn't have the pedal to WOT that it would have decreased my numbers that significantly? And yes, I do not have any cel lights or anything and the car seems to run pretty well to me. Vacuum seems good as well at about 10psi at idle!

 

yes because to have compression you need full volume of air. Any knowledgeable mechanic would know this but I have seen it not done right before. The only thing is I dont think not doing that would affect the leakdown test results.

 

a dyno test would be interesting, but ya get that ring info to us.