Bypass/blow off valve

KZXP398

MEMBER
2007 SAAB 9-3
2.0L
4 CYL
2WD
AUTOMATIC
158,500 MILES

Turbo went out a year ago, previous owner replaced. Turbo went out again. No boost, lack of power, past 3,000 rpm's the engine chokes (figure a bad turbo restricts exhaust pretty badly.) The boost dial (factory) reads some boost. Suspected engine sludge causing second failure. Gave the car to me, signed title, I drove it home. Just started looking at it, the bypass/blow off valves vacuum line was not attached to the turbo. Would this not cause over boosting, as opposed to no boost? There was no smoke before, I started it after attaching the line, smoke. Looks like it suddenly burned oil, then ran rich. Should I look at the valve being bad, or stuck open, or just go with the original plan and pull the turbo and start rebuilding?

3 Replies

STEVE W.

MECHANIC
13,573 POSTS

The bad/removed line would cause excess boost until the turbo itself failed. The smoke is likely oil from bad turbo bearings. That oil can easily damage a converter which is probably why the line was unplugged. I would pull the turbo and go through it/replace it. Engine wise I would run compression and leak down tests just to see what shape the engine is in.

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Wednesday, February 21st, 2018 AT 6:28 PM

MPONT42

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1 POST

Hi, I have an 2004 Saab 9-3 arc. I am experiencing very similar problems with mine. If I put it in neutral and put the gas pedal to the floor it only revs to 4,000 rpm's. And there is very little boost, as if it even has boost at all. So I replaced the coil packs, and spark plugs, only to find out that the cylinder one spark plug chamber was filled to the top with oil. So I turned the car on and a bunch of white bluish exhaust poured out the back for about two minutes while the engine misfired. Then I drove it, it bogged down and would not accelerate past forty five mph, then all of a sudden I felt a jump and some stalling, and boom it ran just fine after that. No misfire, and the turbo was boosting, very strange. If anyone could help me out with what it might be that would be great, thanks.

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Thursday, May 24th, 2018 AT 1:26 PM

STEVE W.

MECHANIC
13,573 POSTS

Most common reason for oil around a plug in a well is a bad valve cover seal. That will cause misfires and those will cause the engine management system to shut off the boost by holding the gate open or restricting fuel or both in an effort to protect the engine and exhaust system.
When you drove it the misfire finally cleared and the system reactivated fully. Prior to that it was in what is considered "limp mode". That gives you enough power to drive it off a highway or to get it to a shop but limits it so that damage should not happen.
I would watch the plug wells because you did not say you replaced the seals and the oil will very likely return.

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Thursday, May 24th, 2018 AT 2:26 PM