4g63 motor issues

[DPARTD]

Hey guys got a 4g63t motor buyer has told me its a forged bottom end but neva gave me recipts but bought the car with low compression from what the previous owner said, now i had my friend do a compression test and each cylinder came to 70psi each one!.... now what does that mean ?? pistons are fine and valves are bent?? just need some ideas guys......

its running a microtech computer, car use to turn over but never reved over 1rpm sounded like it was choking and only time it would stay on is if i had the throttle all the way down and if id let go it would turn off....

 

[EV0300]

what that means is it needs a rebuild, its hard to tell what is exactly wrong with it without hearing it is it knocking? could just be rings crapped themselves, best to pull the head off and have a look would be my advice.

 

[4piknup]

Wet compression test please. Redo test with a spoon of oil in each cylinder.
If results are higher, then rings are the problem, if not then problem is topend related, either bent valves or cam timing.

If rings were that bad, is probably really oily on outside from blowby pressurizing crankcase and blowing seals. Throttlebody will be oily from blowby as well.
And it would stink and smoke out exhaust.

Wet test before you pull head, is a bit strange that in low on all cylinders the same, maybe it's been cooked and lost ring sealing?

 

[OLDIE]

Wet compression test please. Redo test with a spoon of oil in each cylinder.
If results are higher, then rings are the problem, if not then problem is topend related, either bent valves or cam timing.

If rings were that bad, is probably really oily on outside from blowby pressurizing crankcase and blowing seals. Throttlebody will be oily from blowby as well.
And it would stink and smoke out exhaust.

Wet test before you pull head, is a bit strange that in low on all cylinders the same, maybe it's been cooked and lost ring sealing?

Can't see a wet comp test helping if all valves bent but if comp improves in some and not others it could be broken ring lands,broken rings or bent valve/s
IMHO a leakdown test is a far better way to locate the problem.

 

[ENGINR]

Sounds to me like it needs a teardown and inspection. Only way to be 110% sure you know what you're dealing with.

 

[Gianni]

Are you 140% sure there enginr

 

[ENGINR]

I'm 135% sure it's the only way to be 110% sure.

 

[4piknup]

How do you tell if it's cooked rings if you don't leak test or wet compression test first.
Sure, if it has holes in pistons or broken lands you can see, but otherwise it pretty hard to see.

It may be as simple as bad cam timing and you all want to pull the head off first.
Do a proper diagnosis before you touch the bolts

Sure, a leaddown test is the best option, but a wet compression test is second and the op mate already has a comp tester.

 

[Entaran]

I think the relevant point here is it's fucked.

Tear it down and enjoy what you find.

If you're not handy with engines, I would strongly suggest you give it to a mechanic to tear down. 4g63's (once worked) are very... touchy and have many points of failure.

 

[BMGTZ]

70 psi?....check compression gauge isn't fucked before doing anything else!! I am surprised it would even start on a normal starter.....usually something that low would need to be towed to start it.

symptoms seem like bent exhaust valves from your description tho

 

[Gianni]

I tOok the he's off for him on Friday. Pistons had huge ass dints from valves. One had a chip. A few slightly bent valves but I've seen worse. And timing belt I could wiggle off by hand :s