Possible Boost Leak? Need help!

907 Views 4 Replies 2 Participants Last post by dzeiler, Oct 13, 2001

Discussion Starter · Oct 12, 2001

I am having a problem with boosting that is getting progressively worse. I finally put my GReddy electronic boost gauge in, and it seems I'm hitting just about 0.5 bar, and that is with a Profec B installed and turned all the way up. The only time I consistently hit even 0.8 bar (stock) is when I ran with the wastegate hose unplugged for a few miles.

I just took apart the intake tract and and checked the 3 hoses after the intercooler plus the easy one coming off the turbos. I did not get to the one attached directly to the intercooler inlet because I wasn't sure how to remove the shield. I'll probably have to, though, to make sure its not that hose leaking.

After I reassembled everything I was able to hit 0.8 bar in 4th gear on the highway on the way to the gas station, but on the return trip it wouldn't go past 0.5 bar again. Then I pulled the wastegate hose and was able to get 0.8 bar in 4th again.

What I'm wondering is, is there anything else that could cause that much pressure loss short of an intercooler hose being loose? I think as a precaution I might just go ahead and order and install that silicon hose kit they have at MVP, just to eliminate the possibility of vacuum leaks.

Thanks for your help.

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Grant

· #2 · Oct 12, 2001

Yes.

Look here: http://www.mkiv.com/specifications/ncf/ncf93/

Read from pages 88 on. If the sequential system is messed up, it won't boost much past .8 bar. You can follow he hose diagram on the underside of your hood and the description of the system in the link to help troubleshoot the problem.

Once you've realized all the silly things that can go wrong, look for the TTC mod in the tech articles section

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dzeiler

· #3 · Oct 12, 2001

There seems to be a bunch of people with the same or similar problems surfacing. the cause of the problems is most likley in the complex system which causes the car to go into sequential mode. Check the actuator to the EGCV check the actuator to the IACV check their vacuum hoses( I recomend people with older cars replace thier vaccum hoses anyway check out (www.hosetechniques.com) if those check out other causes could be a bad pressure tank or bad vsv to the egcv or Iacv. Use the resource \grant mentioned for information on how to check the various systems I mentioned \also go TTC if the problems disapper this confirms it is one of the systems I mentioned above.

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Discussion Starter · #4 · Oct 13, 2001

Made some progress...

I checked the last intercooler hose, the one attached to the intercooler inlet. No dice, it was on tight. I tightened it a tad just to make sure.

So I was going to do the permanent TTC, but I couldn't get the C clip off the actuator. And, being fresh out of check valves

I just bypassed the Exhaust VSV and the Intake Valve Controller. Yeah, its not perfect, but it had the same effect as check valve way, except they won't stay open, they have to keep opening.

So now the car is happily boosting to 0.8 bar in 1-4 in what appears to be twin turbo fashion. The low end isn't great but the high end...wow...how I missed the boost! I think since TTC is healthier for the turbos anyway, I will use the "temporary" method with the check valves and put screw-type clamps at all connections just to be safe. Unless someone knows a trick to getting the clamps off the actuators...

Sadly, though, I have my Profec B hooked up to the Wastegate (correctly, I double checked it) but it is still not working properly. I don't believe its holding the solenoid closed at all, but I'll have to check. I know the Profec B controller is getting boost because its on the same line as my gauge, which is reading great. The DIP switches are set properly and the electrical connections are solid. The only thing I know to try now is to mount the solenoid upright, as its sideways now, but I didn't think that would be a big deal. If it is, I'd like to know why exactly.

Any comments and advice is greatly appreciated!!

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dzeiler

· #5 · Oct 13, 2001

check your waste gate actuator the spring is probably bad leading to premature closer of the waste gate either that or you have no bcc and the car should hit boost cut. A healthy twin turbo should hit 1.3 bar easily( 19 psi) try this totaly disconnect the waste gate acutuator fromthe sytem be care full you have no boost control now see what you boost to if you get full boost you need a new waste gate acutuator. Alternatively you have to get the solenoid of the profec b repalced.

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