Compression test results

[billyfusco]

I just did a compression test and here are the results 180, 170, 150, 180. I did a wet test on #3 and got 190. Is this a big problem?? Could this cause idle problems? Should i rebuild???

Also i've been trying to track down my power loss and idle surge. Did a boost leak test 3 times a week for months. I replaced the injector o-rings/insulators. ISC, Biss o-ring, TB shaft seals. I'm almost holding 20 psi. But i can find anywhere else it would be leaking from???Could cylinder #3 be my slow leak?

 

[ADrewzki]

If it's holding pretty good, I don't see what the problem is. It's not going to hold 20psi indefinitely. Eventually the air will leak out. if the 150 compression is really bothering you, get it fixed. You can try some MCCC or maybe a can of restore or similar as a bandaid fix and see if that helps. Otherwise, it's still reasonably good compression. Yes, it's lower than your other cyls but personally I wouldn't worry too much.

 

[Fusa]

I've been told that 150 is the dealer's service limit for a 1990, but i don't think it's cause for too much concern. i'm certain it will hold up until you're ready to rebuild your head or block. the low compression is caused by either your valves not completely sealing, or your rings.

 

[ddavisaf]

Dealer service limit for a 1g 4G63 is 121 psi on any cylinder and no more than 14 psi between any cylinder.
It can be caused by rings, headgasket, or valves not sealing.
Your problem will get worse... and you'll have to rip her apart eventually. Start saving money and when the time comes and you hit 120 psi on that cylinder, upgrade.