oily smoke on return to idle

[jonathan yee]

car: st185 gt4
engine : gen3 st205 3sgte
turbo: was ct20b, now gt2560

ok, the issue i have is most of the time when i pull up at lights, a sec after the car returns to idle, a big cloud/puff of smoke will exit the zuast. the amount of smoke and frequency does vary.

initially i thought it was the turbo oil seals gone on my ct20b, so i fitted a gt2560(2nd hand) it seems odd that it would have the exact same problem. it doesnt smoke under load, nor when first starting up in the morning or when idling.

the eng was rebuilt around 5000k's ago. i got the bottom end assembelled by a reputable company, but i stripped and assembelled the head myself and then fitted all pumps and ancil and fitted to my car.

which i'm prob guessing it means i did something to the valve stem seals, except that it doesn't smoke on start up, nor on deccel?

[trdee]

oil backing up the turbo drain?

[thechuckster]

Check that you can suck thru the PCV port in the cam cover and the port inside the throttle body isn't blocked. I got this same smoke behavior when the turbo failed in my barge - valve-stem seals were replaced, turbo replaced (stuffed bearing & compressor-side seal) but fortunately discovered the vacuum port in the throttle body was blocked thus saving the replacement turbo from ruining another seal.

[jonathan yee]

Pcv fine, wouldnt think oil back up as was stock turbo and lines etc before, not overfilled with oil.

Which vac port on tb? The one that goes to charcoal canistor?

[thechuckster]

gen2 PCV consists of a small port in the cam covers near the TB, goes via small tube to a port at lower-left of TB (looking at it from front of car). There is no one-way valve in that system.

charcoal cannister port is on top of TB.

[jonathan yee]

I has gen3.

[thechuckster]

argh ... I haz fail at reading


but the smoke you are describing( high-vacuum-and-return-to-idle) usually comes from:
- PCV and/or crankcase breather blocked
- a valve-stem seal cracked/torn
- turbo oil leak on compressor side.

[George]

+1 for valve seals

[jonathan yee]

not turbo oil leak comp side-intercooler etc clean as a whistle.
i put catch can in line with pcv-manifold- didn't fill up with oil and when i pull PCV form off cam cover with eng running there is strong vac, so not blocked
just changed valve stem seals with new, nothing really found wrong with old, maybe 1 or 2 not pushed down properly but none loose or split, still same prob after fitting new seals

leak down test shows everything is norm, so not pistons/rings, bore scope/camera shows oil on pistons and when doing valve stem seals there was oil on the valve stems and intake port/manifold runner floor, but thats most likely due to the angle of the head, any oil would run back down there, top of manifold/plenum is clean.

looking at possibly the head having issues, possibly leaking down outside of valve stems?????? but why no oil when hard deccel?

and no i don't have the ISCV hooked up to the sump....LOL