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Boost control valve testing

1368 Views 75 Replies 7 Participants Last post by  BobSaabit
I'm trying to troubleshoot low boost on my 2000 9-3 SE (b205r).

I've seen some contradictory information on troubleshooting. If I disconnect the electrical connector will the waste gate stay shut?

I'm Checking the bypass valve (B235R, B205L/R) – 9-3 2000 | SAAB Workshop Information System Online it talks about troubleshooting the Checking the bypass valve (B235R, B205L/R). Is this the vacuum operated part that actually connects to the waste gate via the pushrod?

I assume that if I disconnect the vacuum line from the part that actually connects to the waste gate via the pushrod that the waste gate that the waste gate will remain closed also.

Thanks,
Eric
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Discussion Starter · #3 · (Edited)
Nope, car is in base boost mode.
In both scenarios I listed it will be in base boost mode?

Is there a way to fully close the waste gate?

Is the "bypass valve" the vacuum operated part that actually connects to the waste gate via the pushrod?

Also in Basic boost pressure control valve setting – 9-3 2000 | SAAB Workshop Information System Online it talks about a seal on the pushrod. Is this seal something to indicate tampering with the boost or is it a seal to prevent leaks, etc?
 

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Why you want to close wastegate?
Yes, disconnect W hose and leave it open. THIS IS FOR TESTING ONLY, DO NOT DRIVE WITHOUT WORKING WASTEGATE!
 

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The vacuum operated bypass valve is different than the wastegate actuator. As Mimmi states just do a test with the hose disconnected. The wastegate is opened by the pressure produced by the turbo. The boost pressure control valve bleeds off some of that pressure to get you from base boost (about 6 psi) to full boost (between 9psi and 15psi depending on factory settings). By removing the hose the wastegate will remain closed and boost to unsafe levels. If you would drive this way you will be putting in pistons or valves when they burn.
Remember your boost gauge in the car is not reading the psi of boost. It is based off how much air is going through the MAF. If the MAF is failing it often reads low. So it is not putting in enough fuel. So if you undo the wastegate you can burn up the valves or pistons even quicker if you try to drive it that way.
If you have full boost with the hose disconnected you might need a boost pressure control valve. If you still have low boost you might need a turbo.
 

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The Boost gauge is Directly connected to manifold pressure.
Map is also reading Mani pressure directly. the two are NOT airline connected.
Pull the W hose off the Boost control solenoid as a test to see IF your system is capable of generating max boost.
The Fuel cutoff pressure will be hit if it is....as evidenced by a total loss of Go! at that point ....an Unmistakable event !
Do not hit that fuel cutoff event.. too many times ..as it's hard on the mechanicals though.
 

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Even though T7 has a Map sensor it is not used for the Turbo gauge in MIU. It is used mostly for self diagnostics. If you look in WIS under MIU and go to the description for the Turbo gauge you will see if uses the MAF for the reading.
 

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Probably a doodad that reports the MAF is easier and cheaper than running a vacuum line from the dash board to the engine.

In the '80s when the turbo operated largely independently of engine management and was substantially less reliable, a turbo gauge was possibly informative.

In modern-ish cars where the turbo is a reliable component of comprehensive engine management a gauge is little more than entertainment. I don't have one in my Solstice or GTI and have never once missed it. Even in the 9-3 Aero I don't even remember a time where I've looked at it. The only time I specifically remember looking at it in the Viggen was when it was suddenly down on power - due to a MAF failure.

The number of times I've taken c900s apart to replace vacuum hoses in the dash is more than I'd like to count. The number of times I've taken 9-3 dashboards apart is zero.
 

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Discussion Starter · #12 · (Edited)
Im seeing a max of 1 psi on a cell phone app from my OBD2 adapter. I wonder if this would be from the MAF sensor or actual manifold pressure. It reads inches of vacuum at low throttle then psi of boost at higher throttle.

It sounds like disconnecting the electrical connector on the boost control valve would have me at base boost and disconnecting the waste gate vacuum hose (from either end?) will totally disable the waste gate?
 

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That's correct.

It's hard to guess what a generic OBDII adapter shows. My Scangauge will display MAF in g/m and MAP in psi, but I have no way of knowing whether those are actual sensors or calculated values. I assume sensors but I don't know. This is an area where Tech 2 is helpful. It can also show MAF deviation, which tells you the variance of measured and corrected mass air... it's very helpful for diagnosing failures.

If you are actually getting 1psi, that is below base boost. The only way to get that is if the turbo's wastegate or actuator is defective or the engine is running real bad or there is a massive air leak. You can check the first with a Mityvac and a visual inspection. Second doesn't sound like it's the issue. Unhooking the W port will test the third, so would a smoke machine or intake pressure tester, either of which are the far safer options.
 

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Discussion Starter · #14 · (Edited)
That's correct.

It's hard to guess what a generic OBDII adapter shows. My Scangauge will display MAF in g/m and MAP in psi, but I have no way of knowing whether those are actual sensors or calculated values. I assume sensors but I don't know. This is an area where Tech 2 is helpful. It can also show MAF deviation, which tells you the variance of measured and corrected mass air... it's very helpful for diagnosing failures.

If you are actually getting 1psi, that is below base boost. The only way to get that is if the turbo's wastegate or actuator is defective or the engine is running real bad or there is a massive air leak. You can check the first with a Mityvac and a visual inspection. Second doesn't sound like it's the issue. Unhooking the W port will test the third, so would a smoke machine or intake pressure tester, either of which are the far safer options.
My initial problem was my car wouldn't start when it stalled out. Initially it sounded like a crank position sensor. Then it died while driving on the highway showing a P1105 and a P1300. Now the turbo is very loud and doesn't seem to have any boost.

I wouldn't think a massive boost leak would stop the car from running altogether, maybe I have more than one problem.

I think I'll look at the boost issue now since it's reproducible. I've seen some videos on how to make a a boost leak detector. It looks like I also check the waste gate and end play of the turbo without removing the turbo from the car.

I've had the car a month or so, it ran pretty good for several hundred miles. I got 32 mpg driving it from Virginia to North Carolina. It seemed to have similar power to my wife's 2004 9-3 convertible.
 

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My initial problem was my car wouldn't start when it stalled out. Initially it sounded like a crank position sensor. Then it died while driving on the highway showing a P1105 and a P1300. Now the turbo is very loud and doesn't seem to have any boost.

I wouldn't think a massive boost leak would stop the car from running altogether, maybe I have more than one problem.

I think I'll look at the boost issue now since it's reproducible. I've seen some videos on how to make a a boost leak detector. It looks like I also check the waste gate and end play of the turbo without removing the turbo from the car.

I've had the car a month or so, it ran pretty good for several hundred miles. I got 32 mpg driving it from Virginia to North Carolina. It seemed to have similar power to my wife's 2004 9-3 convertible.
P1105 is a lack of boost (charge air pressure). A very serious lack. It should not cause the car to stop running, it would just run very sluggish. The most common reason would be that an intercooler hose blew off. They can look like they are on and actually be blown off the fitting, so you need to get a hand down there and check on the output side.

P1300 is random misfire, typically misfire on multiple cylinders.Misfiring bad enough to dump raw gas into the cat and be a concern. I would expect that it would be accompanied by some additional cylinder specific codes. But that's not guaranteed, I'm guessing. The most common reason for that would be a bad DIC and/or plugs.

Is the DIC old or unknown? Plugs? If you pull the DIC off, there's a date code on it. If you have some vehicle info from the sale, perhaps you can estimate the miles on it. If it doesn't have "SEM" on the label, it's likely aftermarket and they go bad. If it's OEM, they die round 70K miles.

I'd be suspicious that you have two issues here. The car should run like an underpowered Pinto if the turbo has issues, but it should run fine.
 

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Is the wastegate actuator still attached to the wastegate. That P1105 almost sounds like the code you get when the clip holding the actuator onto the actual wastegate lever falls/rots off allowing the wastegate to get stuck in a fully open position.
 

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Discussion Starter · #17 · (Edited)
Is the wastegate actuator still attached to the wastegate. That P1105 almost sounds like the code you get when the clip holding the actuator onto the actual wastegate lever falls/rots off allowing the wastegate to get stuck in a fully open position.
The wastegaye linkage is still there. I tried disconnecting the electrical connector to the bypass valve and got no boost. I tried disconnecting the W vacuum line from the bypass valve and got no boost (do I need to plug the line or cap the hole in the bypass valve when I do this?) . I think I have a big air leak ( although everything LOOKS OK) or a dead turbo.

I assune the wastegate and divertor valve shut when at rest, like when the engine isn't running. Is this correct?
 

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Reach down where the hose that comes from the intercooler and goes to the charge air pipe is and check it with your hand. Looking isn't good enough because when it blows off, it stays roughly in place but spews all your charge air under boost .

You don't need to plug the W line. It's blowing air out, not pulling it in. You can if you want to but it shouldn't matter in the context of testing the turbo hardware.

Wastegate is shut when engine is off. Or at least it should be. Reach down there and try to move the lever. It should be very hard to pull. When the engine starts, it should stay in the same position with the W hose disconnected.

If you want to actually see the wastegate to verify if it's closed or open, you would need to remove the downpipe. That's only three nuts on the turbo studs, but if they haven't been off in a long time they can be a real PITA - especially the bottom one on your T7. You need a short handled 13mm wrench and some time. It's usually about 1/8 turn at a time, flip the wrench, another 1/8 turn, etc. A small MAPP gas torch helps. Soaking with PB Blast or Kroil or similar over three days before helps.
 
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