SMOKE: Suddenly at idle, clouds...

[Craig 930 RS]

Scenario: Friend has a 1983 930, 3.4 motor all professionally rebuilt 4000 miles on it. Went for a drive yesterday, and when we got back to his garage - at idle suddenly there was a lot of smoke coming out the back.

So here is what I noticed:

The car ran perfectly at idle with the smoke

Smoke did not seem intermittent and acted as as if it was a constant source rather than one cylinder (?)

Turbocharger looks dry

When we shut the car down, it wouldn't restart, in other words it wouldn't catch again

What the heck could this be? If you got experience with this kind of thing I would love your technical help :-)

[kenikh]

Did it smell like oil? The turbo could blow an internal seal and not leak externally.

[Craig 930 RS]

The smoke did, yeah. The question I have is where would the oil source come from if the hot side and cold side of the turbo itself is NOT wet with oil? STUMPED!

[kenikh]

You mean you have looked inside the turbo (hot and cold side) for oil, or just an external inspection?

[Craig 930 RS]

Yes, in & out didn't see anything unusual...............

[Mick_D]

White or black smoke?

[kenikh]

I recall some cases where oil would push past a bad hotside internal seal when under pressure only. If under boost, the oil would likely instantly vaporize, leaving little to no residue. But the kind of smoke you are describing sounds like it was getting into the combustion process. This is just a guess.

The fact that the car won't start is puzzling. If there was massive oil intrusion into the cylinders and the plugs got coked up, could be the reason it isn't starting. Have you looked at the plugs?

[Craig 930 RS]

Haven't looked at the plugs yet, the smoke was bluish for sure, I pulled the turbo for him because I can now do these in my sleep :-)

[kenikh]

There's only a few ways to get enough oil into the motor at a volume that produces that much smoke. Most of those come from the intake side.

Let's try the stupid simplest option - was there a recent oil change? If so, was it overfilled? If so, you'll be blowing raw oil right into the intake on a stock car, especially under boost.

If not, then let's walk through the possibilities:

We've checked the turbo and don't think that's it.
The motor is a fresh build, so the likelihood it is leaky valve guides is near nil.

Could it be a broken piston or rings? Check your oil filler for pulsing.
Could the oil scavenge pump be on the fritz? A bad scavenge can force through the seals on the turbo. I know you've checked the turbo, but...no stone unturned.

[pkabush]

I think Kenik has offered sound advice. As you're clearly aware, the turbo seals or the feed line ball bearing, (or lack there of) or scavenge pump is usually the culprit when our motors smoke excessively. Not only have you crossed most if not all of these issues out, to my knowledge, none of those things will prevent the motor from starting. I think the plugs will show something. Might be a good idea to drain the oil as well. If the magnet doesn't show anything you might pull the sump screen.
Is it making any nasty noises when you crank it ?

[Craig 930 RS]

No weird noises, I think the no start is from the motor getting excessively oiled / plugs fouled......all a guesstimate until I get over there to see what's up

[Alan L]

Pulling the IC and looking for oil intake may be useful.
Alan

[jbrown]

Originally Posted by kenikh

There's only a few ways to get enough oil into the motor at a volume that produces that much smoke. Most of those come from the intake side.

Let's try the stupid simplest option - was there a recent oil change? If so, was it overfilled? If so, you'll be blowing raw oil right into the intake on a stock car, especially under boost.

If not, then let's walk through the possibilities:

We've checked the turbo and don't think that's it.
The motor is a fresh build, so the likelihood it is leaky valve guides is near nil.

Could it be a broken piston or rings? Check your oil filler for pulsing.
Could the oil scavenge pump be on the fritz? A bad scavenge can force through the seals on the turbo. I know you've checked the turbo, but...no stone unturned.

I had a shop once forget to hook up my wastegate line and my car overboosted and cracked rings. The funny thing is the car still ran great and did not smoke at all.
I was going thru a quart of oil every 2-3 weeks. I used synthetic oil. If you think you have an issue with broken rings, while the car is idleing take off the oil fill cap and see if you have rhythmic smoke coming out. That is a sign of cracked rings.

[Hams930T]

He overfill it?

[pkabush]

Originally Posted by Hams930T

He overfill it?

Wouldn't account for the no start situation. Although unlikely, it's possible that the two are completely unrelated. Perhaps it was overfilled and there's a blown fuse/relay or disconnected/faulty over boost sensor etc. My armchair internet guess is that the plugs and or draining the oil are going to be the key to unravelling the mystery.

[kenikh]

Sure it could. Overfilling and thus dumping a tone of oil into combustion could coke the plugs and keep it from starting.

[pkabush]

Originally Posted by kenikh

Sure it could. Overfilling and thus dumping a tone of oil into combustion could coke the plugs and keep it from starting.

Ah, hopefully that's the problem.

[Alan L]

I'm waiting at this end on the edge of my seat.
Alan

[kenikh]

Originally Posted by Alan L

I'm waiting at this end on the edge of my seat.
Alan

No kidding! I can't start my weekend until this is resolved!

[Ronnie's.930]

I'm willing to bet Mr. 70'sbush's bush, and Kenik's headstuds, that the turbo seals and bearings are smoked and that Craig just hasn't looked hard enough yet.