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Discussion Starter · #1 ·
Hello all,
Can't seem to find a thread for my exact problem so I'll just make my own, and if there is one, feel free to redirect me. Ok, here we go, I have a 1998 9k CSE with a 4spd autobox. The turbo spools up fine (boost gauge doesn't work however so that's no help). However, if I'm at half throttle or more, and the car gets on boost and when I'm around 3k-4k RPM, the RPMs kind of waver and you can hear the car dumping some of the boost, climbing back to approx. 3500 RPM, dumping again, and if I keep pushing, the car gains boost and then begins to buck violently like I'm hitting a rev limiter or something. I think it may be the T5 BPC Valve, but would like a second opinion and there are no reliable European specific mechanics in my area.

Thanks!
Mason
 

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bucking

If overboost occurs then the ecu will cut the fuel. Car feels as though an anchor has just been thrown out the back. That's what will happen if
the wastegate does not actually open on overboost. Get under the car when its cool !! ( very near very hot exhaust and turbo ) and check the mechanics of the wastegate and actuator.
That's the cheapest, and easiest fix ever. Otherwise.... go for the esoterics,
which someone is probably about to advise you.
 

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If your boost gauge is not working, it most likely means you have a vacuum/boost leak as the gauge is mechanical. It should be easy enough to find, I would fix that personally. It isn't very accurate however it is still helpful in situations like this.
 

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I would virtually guarantee your issue is a failed Boost Control Valve

Like this but for the 9000 (This is a valve for the T7 system and NOT compatible but I couldn't find a 9000 link)
The valve is mounted ion the top right of the raduiator.

A common failure.
Gentle acceleration is ok but the moment you try a little serious pedal pressure the car jerks.
 

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Discussion Starter · #5 ·
Thanks!

Thanks guys! I'll check the wastegate, and I was gonna replace the bulbs in my gauges anyways, so I'll see if the gauge is disconnected on that end (because it doesn't move at all). It'll probably end up being the BPC valve but who knows? Also, if I may I ask, would you guys recommend just getting the correct valve? Because Eeuroparts makes a conversion kit to the T7 valve, though that renders all but their tuning set ups moot... Thanks again!
Mason
 

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Discussion Starter · #7 ·
I thought the Eeuroparts valve replacement (which includes ECU tuning for it) would take care of it? Is the T5 really that unreliable? I was looking at it fiscally, that the conversion kit is cheaper than replacing the valve, is supposedly better, and if it did break, the T7 is a fraction of what the T5 costs.

http://www.eeuroparts.com/Parts/52650/T5-BPC-Update-Kit-T7-Valve-101K10078/
 

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How easy or difficult should it be to move the wastegate 'solenoid' actuator when the engine is off and cold? Any telltale signs that it's buggered, apart from not being able to get it to move at all? I presume it's a spring-loaded device and the change in vacuum moves a plate against a spring to move whatever the rod is joined to.

As for the APC solenoid valve, what tends to be common failure symptoms and modes for those? My 9k has a strange sort of surging/bucking under power especially at lowish road speeds, so curious if it could be similar to the OP's issue.
 
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