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01 Turbo - Boost Leak? Loss of acceleration.

2109 Views 8 Replies 4 Participants Last post by  billymade
Hello everyone! First off this forum is awesome. It's been rather fun checking out all the posts on this website in the past few weeks. I'm new to the forums and can use some help.

I recently purchased an '01 turbo beetle with the APH engine. I previously had an issue when I had no acceleration and the EPC light came on. Thanks to the threads I found. I was able to fix by cleaning the throttle body. A couple weeks later and I have a new issue. Seems like the beetle has lost some punch. A couple days ago it seems like the the car is struggling. It accelerates okay but not like it used too. I can floor it and I don't see much improvement. It seems like I loose power around 3000 rpm. I think I may have a boost leak. I don't believe it is the turbo. I can hear it spool when reving in neutral. No CEL light.

This is what I have done so far.
I clean the throttle body (I thought maybe I was having the same issue as before)
I clean the throttle body sensor
I clean the Mass Air Flow sensor
I visibly checked for cracks in the hoses
I checked the diverter valve by taking it out and pushing the spring up and placing my finger on port where the vacuum hose goes, it held the spring open.
I made one of the boost leak testers where you attach an air line to a plug and pressurize after the MAF. I did have the pcv removed and plugged the hole. I did not hear any leaks besides the oil filler cap, I did hear what sounded like bubbling oil (is that normal)?

I could use any ideas you have to help solve the problem.
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I had a problem with my diverter valve and it was sticking/actuating slow but did not have a hole in it. So, the conventional testing methods; did not work, as it was still holding vacuum. If it is the original DV; I would replace it.

Check out my thread and see if what I was dealing with, see if it is similar to your problem.


Aside from that; if you have access to a scanner with live data, your fuel trim levels can help diagnose things.

Hi Billy, it is the original diverter valve. I will replace it and see if that helps. I do have a scanner and I use VCDS-lite. Not sure if that has live data.
Thanks for the link. I've lost daylight for the day. I will take the hose off tomorrow and inspect it. May have been something on the back side I missed.
I would check part number 058133753D. It tends to crack at the seam where the plastic comes together. It lead to poor performance for me, rough idle, boost leak codes. I would also try a throttle body adaption if you have cleaned the part.
A picture of the part number listed above for reference - https://www.ecstuning.com/Volkswagen-Passat_B5-FWD-V6_30v/ES2681254/

These are usually for the power brake vacuum on most of German cars, not 100% if this is in the power brake line for the NB Turbo.

I think I may have found the problem. I think there was a vacuum leak on the set that goes to the diverter valve. I found the rubber 90 degree connector that connects the vac line to the plastic piece above cylinder 1 and 2 had split at the plastic piece side. I replaced it with an inch or so vacuum hose and it seems to do the trick. I'm getting better acceleration and response. I think I may still replace the diverter valve down the road. Thanks for the help and suggestions.
Cool, glad you found a primary boost leak; on the DV, after 14 years or so, I would think the original one is definitely worn or possibly sticking. You might check; all the other boost related hoses as well.
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