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Turbo Boost Pressure Solenoid Valve Vacuum Lines Disconnected


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#1 mneag

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Posted 20 September 2011 - 03:09 AM

Thanks to everyone who has helped out in the past. I was doing maintenance on my new-to-me R this weekend, and noticed something peculiar. A previous owner had installed a K&N cone filter (removed the airbox), so I took it out to clean it and found something underneath with vacuum hoses that were disconnected, but it was still connected to the wiring harness. I did a Google search on all the numbers printed on it, and found out it was the "Turbo Boost Pressure Solenoid Valve". Is this what everyone around here refers to as the TCV - Turbo Control Valve?

Here's a picture:

http://www.fcpgroton...rge/9473212.jpg

Anyway, this sounds kind of important since I'm sure over-boosting is detrimental in the long run. So, I did plenty of other Google searches and found this page:

http://webspace.webr...keithspage.html

According to this page, I guess it's possible to bypass the ECU controls with a "manual" boost controller. What would I look for to find out if someone has done this? I tried looking for the vacuum connections to the turbo, but they are hidden underneath the heat shield (do those come off and back on easily?). What I thought might have been it, I think is probably the air pump connection (purple vacuum hose).

I had accidentally left the part on the bench when I moved the car, and now the CEL light is on, I guess because the ECU couldn't see the valve. It wasn't on before.

I also found a boost guage behind the radio, so I did some driving to see if it was over-boosting. I'm not sure if I was able to give it a great test because it was raining and the industrial park that I was test driving in has short roads, so I couldn't safely hammer it for long distances while driving on wet roads and looking down the radio hole at a boost guage. It jumped up to 20 once, but then dropped back down to 10. I'm not sure if the TRACS system was retarding the timing 'cause the wheels were spinning, if the ECU detected detonation, if it's normal, or just something else. This is my first turbo car, so I'm not entirely sure what to expect.

So, two questions:

1. If I don't find some "manual" boost valve controller thingy on the turbo, should I work to hook this valve back up? I'm guessing so. All the color is gone off the vacuum hoses, so I've got to try and see if I can find diagrams (haven't got VIDA or VADIS working yet). What kind of damage could this being disconnected cause?

2. I'd like to pull the codes to find out what the codes are. I'm thinking of using a VAG-COM cable and the demo version of VOL-CFR (I know I can't clear them with the demo, but right now I just want to know what they are). Does anyone have a similar set up, or can they recommend something else?

Thanks!

#2 Ihatespeedbumps

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Posted 21 September 2011 - 12:09 AM

What year is your R?

#3 mneag

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Posted 21 September 2011 - 03:09 AM

It is a 98.

#4 lookforjoe

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Posted 21 September 2011 - 05:36 PM

U380 OBDII scanner, about 30bucks, will access & allow you to clear any/all codes.


20psi spike is not healthy.

TCV routing

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#5 mneag

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Posted 22 September 2011 - 04:58 AM

Can I assume that hose 18 would go to the missing air box?

#6 thomasw

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Posted 22 September 2011 - 09:26 AM

From memory it goes onto a nipple in the air intake pipe shortly after the MAF. Between the MAF and the turbo inlet right on that bend after the MAF.



The one on the right under the bend. I have replaced all my hoses since this picture was taken as they were all cracking like these ones.

No idea what I did to have the picture appear twice. Edit shows the link once?

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Edited by DownundeR, 22 September 2011 - 10:03 PM.
Fixed... IMG inserted twice


#7 mneag

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Posted 23 September 2011 - 12:01 AM

You guys are awesome! I'll try this when I get back in town.

Thanks!

#8 thomasw

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Posted 23 September 2011 - 12:06 AM

Thanks Trent. Let's keep what I do for a living on the down low hey. Could get embarrassing for me otherwise ;)

You guys are awesome! I'll try this when I get back in town.

Thanks!


No problem. If you want then I still have a full set of photos with arrows and labels and stuff DAZ used to piece his vacuum line spaghetti together after he got his new engine.

PM me you email address if you want them

Thomas