Angel

After being plagued with some sort of problem with my car, I decided that I needed to get a compression test done.

The car simply isn't running well. At half throttle, she feels great ~ 8-10psi, very smooth, everything is perfect. At full throttle ... different story ... ~12-14psi, kinda sputtery, no power really, just a big old slug.

So far, I replaced all of the vacuum lines, the cap, and the rotor. The current plugs have 800 miles on them.

Datalogs show 12:1 AFR, 14psi, no knock, good timing, everything looks fine, but the car is slow as hell.

The last time we did a compression test, the motor was cold and the number 6 cylinder came up 30psi short of the other 5 cylinders. I figured my engine was on its way out, but a few friends told me that doing a cold compression test isn't very accurate. I figured since the other 5 cylinders were all close together, my friends were probably wrong. I also figured now when we did the compression test that I probably had some internal damage and number 6 would be toast (like 50psi or something) and that is probably where my problem was.

We warmed the car to normal operating temperature.

batty200 from turboforum.net performed the test.

1st cylinder was about 40psi.
2nd cylinder was about 55psi.

batty200 was ready to give up, said my engine was screwed. I told him I wasn't convinced, please do EVERY cylinder. By the time we finished all 6 cylinders, the highest cylinder was 60psi, the lowest was like 30psi.

batty200 was ready to go home, saying that I blew my headgasket or something, and he said I should just swap in my spare motor. I told him I still wasn't convinced, it didn't make sense, the car runs too well besides under full throttle. So he said we would do a compression test on one of the cylinders in his car, just to prove that there wasn't a problem with the compression guage.

So we did and it yielded 30psi.

Now he agreed with me, and he decided to mess with the guage and after some 3 minutes or so, he had it fixed up.

We went back over to the Lex and did the compression test again.
1- 175
2- 185
3- 190
4- 185
5- 180
6- 180

Considering at this point, my engine had cooled for over 1/2 hour, I am rather pleased and relieved to know that the 2JZ is indeed indestructable. I think that if the motor would have still been warm, the results would have all been 185-190. The #1 cylinder I actually think is higher than 175, my wife was the one cranking and she was just counting to five and stopping. I think #1 was still going up a bit.

Now I just need to troubleshoot some more. New plugs are going in and I guess aftermarket ignition is next ... even tho I just sold my MSD ...

cliffnotes
-cold compression tests are sketchy
-make sure your compression guage is accurate
-2JZ owns all other wannabe engines
-after 9k miles of turbo fun, my motor is still mint
-buy my car right now for $20,000 PLEASE so I can buy a house, thank you

motorheaddown

Angel,

Coupla notes:

1) These numbers seem way too high especially with a thicker hg. Think about it, you effectively *added* volume to the combustion chamber with a thicker hg. That means the compression numbers should be slightly *lower* than the OEM average. The minimum is 156psi: http://www.mkiv.com/manual/manualtt/..._check/ct2.jpg This could only mean that there is *considerable* loss of chamber volume, or your compression meter is off. The loss of chamber volume could only be due to carbon build up. I get 150psi across the board on all 6. I dunno... something just doesn't sound right in your case.

2) The loss of power and spudder could be due to spark blow-out. What are your plugs gapped to? I have mine gapped at 0.030", and I get blow-out at anything above 14psi. A CDI fixes that.

3) How have you sealed the injectors in the intake runner? Using the OEM injector insulators is a *bad* idea. The GE injector seals are designed for vacuum, only. Consequently, the seals *easily* push out at positive pressure in the runner. That will cause spudder, too. Plus, the AFRs and knock won't show any problems. It's something to think about.

For $20k, it's a great price. Someone please buy this car so it stays in the CL family.

-scott

P.S. How the heck did you lay down 400+ rwhp with these kinds of problems? Spark blow-out and injector blow-by won't let you even come close to 400 hp regardless of how much boost you're running.

Angel

First, the answer to your "PS" ... I didn't have these kinds of problems. This just started one day out of no where.

Now, to answer your other stuff in order. I think my compression numbers are perfect. They match the numbers that I had last time we did a compression test, using a different guage, only this time, number 6 kept up DaveH has a 3mm headgasket and he goes 160+ across the board, I have a 2mm, I think it makes perfect sense.
*edit* just copied from SupraForums ...
My plugs are gapped to 0.028". I am going back to 0.030" this time. I can't use a CDI I don't think because I still have my distributor.

As for the injectors and the intake runner ... I have no idea Is there a way I can check ? I wasn't around when the fuel system was being done

And yes, I think my price is very reasonable

Thanks for chiming in

motorheaddown

Buy some cheap powdered, spray deoderant (sp?), and spray it on the injector seals. Cheaper, the better. Take the car for a spin and see if the powder gets disturbed. A leaky injector seal will blow the powder out of the way. Clean with carburator cleaner when you're done.

-scott

Angel

Thanks for the tip. As soon as I get her put back together (probably today), I will give it a shot and see what happens

JPI Racing

Your compression readings are perfectly fine. Did you do a leak down test?
JPI

awj

Angel - CDI means capacitive discharge ign. Perfectly doable on the distributor ignition. This what the old cats run. It's just multispark and more current/voltage. Putting a better coil might help too. You might have to modify your cap a little. Nothing major. CDI becomes a challenge when the distributorless ignitons feature coils with individual and integrated drivers (or ignitors). With an external driver, the cdi will work as well with DLI's.

Back to basics though. What do the plugs look like? I'm running oem fuel set-up at the rail. I don't see these problems either. That's not to say they don't happen.

Angel

JPI, no leakdown test yet.

awj, I will be reading more into the CDI soon as well. The plugs were perfect, I mean PERFECT, looked like I just put them in 1 mile ago.