Ok, I'm Stumped

[zebra]

Hokay,

lend my your ears eyes,

New car is down on compression on the number 5 jam pot, but I don't know why!?!?!?! it came up at 88psi when the rest were 150-160

The car has dodgy valve stem seals, so blows some smoke after idling for a while, but that is unrelated to the lack of compression. (or is it?)

I initially thought the rings were shot, but it doesn't blow smoke under load and the motor is very quiet, has very minimal blow-by and feels quite strong and smooth, idles smoothly yadda yadda yadda.

It is a dead stock 1JZ with a cat back, standard boost factory intercooler etc.

Now to my theory, is it at all possible that the leaky stem seals have gummed up the back of a valve which is causing it not to close/seal properly? I'm sure it is possible, but I have never seen/heard of it in person.

Now when my RB25 chewed up and spat out a ring, the smoke would increase with revs/load as well as showing obvious pulsing blow-by.

I'm going to try and borrow another comp tester and squirt some oil in the bore to double check (I didn't have anything handy this morning)

But like I said, no smoke under load, to me it doesnt make sense.

So I hope you can help too a) put my mind at ease and b) save me from having to buy a new motor

Cheers

A

[rob82]

Totally possible - leak down test time.

[blk94r33]

Totally possible - leak down test time.

+1

Very easy to make with an old spark plug, air line fitting and oxy......

[TiTAN]

driving behind you yesterday there wasnt even a hint of smoke all the way to where i turned off.

[zebra]

So, easiest way would be pressurize the cylinder and listen in both the intake manifold and the tail pipe for the hissing?

I would but my air compressor is at my old mans house 1100ks away lol

Titan - yeah, only smokes if its idling for a while, if you blip the throttle after idling you get a big puff of blue oily smoke.

[GTR_JOEY]

When u first start it up does it blow blue smoke and miss fire... then get better as it warms up?

[zebra]

blue smoke yes on both hot and cold start, no miss-fires, even at WOT (warm)

[Duncan]

smoke sounds like a turbo oil seal (early). a little leaks down the dump while off, then starts to burn out once hot. it can seal up under boost depending on where it is farked so no smoke then.

nfi on the compression.

[zebra]

I had considered that, but it the smoke is too instant after starting cold, and I'll be f**ked if I am pulling 1J turbos off ever again! lol

I will pull the cooler piping off tomorrow and have a squiz, but 20 years of crank case gasses being sucked into the intake pipe means it will be oily

[GTR_JOEY]

i was goin to say just before mine let go it would blow blue smoke on start up and miss a bit...then as it got warmer the smoke would disappear and the miss would go away as the rings sealed better

if urs isnt missing at start up then its not the same case as mine...

[zebra]

Yeah, it has me beat

Will get a leak down test done asap, I really am hoping it is just the head causing the problems

[Gerg_R31]

Valve stem seals would explain the smoke / burning oil on start up,

the burning oil may have glazed the bores and your leaking compression past the compression rings, preventing a proper seal with the glazed bores, but your oil control rings are still sealing to explain why your not consistently burning oil

leak down test / wet comp test will help

May also be leaking passed the head gasket giving you low comp

[zebra]

Ahh I didn't even think of the glazed bore issue,

Wish I had a bore scope, would be nice to have a look inside

[The Dan]

There is no use over-complicating the issue. It's practically a dead stock 1JZ....the likelihood of glazed bores is so remote, it is literally the last thing you would consider. That and the fact it would smoke all the time if that were the case.

You definitely need to do a leakdown test before you can make any assumptions. It could even be a worn valve guide causing the valve to seat incorrectly AND make the stem seals leak - also not likely on a single cylinder

Remember when you are doing the test to have it at TDC Comp on that cylinder

[zebra]

Cheers Dan

just popped the cooler piping off and it is dry as a bone,

So leak down test coming up asap

[BOZ22N]

Omg it starts again :-(

Are you fouling any one plug? Or is one wetter than the others?

Just drive it for a while and monitor it. Stop pulling stuff apart.

[zebra]

No plug noticeably worse than the others...but they did look fairly old, no misses,/coughs/splutters at all.

So will keep an eye on it and see how it goes until I can get a leak down tester on it

[Manuel Kasko]

Just give it to me.

I could keep it try fix it.

Problem Solved

[zebra]

So the plot thickens.....

These are the same plugs that were a little oily the other day...cleaned them up and put them back in.

Pulled them out again today...

looks a lot like rust to me

compare these to one from the Soarer

The orange plugs are BRK6EP's

cyl 1 on the left and 6 on the right

the plug from the soarer is a BKR6E

found my little high power torch so had a look down the plug holes, piston crowns are dry, and also have a slight brown/orange tinge, No sign of any oil in #5, they all match evenly.

So I am thinking that Duncan is correct in saying that it is a turbo seal, Causing my smokey exhaust

Doesnt explain the lack of comp in #5, but I may have muffed the test, there was a bit of crap around the #5 plug hole that may have caused the tester to leak

The car doesnt seem to use any water, but I havent owned it long enough to say for sure, the oil is about 400ks old and looks brand new, so I think that if it was rings the oil would be a lot darker

????

Any more ideas

[SargeRX8]

Oil can dark a few hundred kms after changing even on a healthy motor. You are right to say though that if a ring was fine, the piston won't be sealing and carbon and other combustion shit could make it's way into the oil.