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Boost issues, HELP! Experienced mechanic here

1K views 14 replies 5 participants last post by  zak99B5 
#1 ·
All right fellow 1.8 T owners, here is where I am at with my car. I recently picked up a B5 Passat at a really good deal that had a few issues, the PCV breather hose was broken along with some coolant lines. I did the necessary repairs and the car is running great. My issue is I was only pushing 2 pounds of boost, so I did some research and I read that the n75 can throw off your Boost if it is bad. I unhook the line going from the n75 to the wastegate and I also ran my compressor at about 20 pounds through the wastegate to clear out any possible carbon. So in a nutshell when the car is cold and I take it for a burn it starts to school around 3000 RPMs and will hold 6-8lbs up to 5500 RPMs easily. When it is warm I realize that it struggles to get the 8lbs. I'm a marine mechanic by trade so I'm no dummy, but when it comes to turbos I'm clueless. Does this sound like a boost leak, bad PCV valve, a bad wastegate / Turbo? Somebody please help because I am really pulling my hair out. I am planning on ordering the aw E tuning kit with the k04s but prior to doing that I would like to get this one running right this way it is a matter of installing the new components and having no issues. I've also got another issue that is a bit off topic but maybe somebody can help me, I also have a CEL but my code reader nor any other code reader won't read the codes. I have heard it could be a bad ABS controller, but if you unplug the ABS it should be able to link up? So far no luck. Any advice is appreciated criticism please go away lol
 
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#2 ·
First a question; how did you blow air through the wastegate to clean out carbon?

Wastegates are kind of an unreplaceable wear item, and with an old 1.8T that could easily be the situation. A new turbine housing or complete turbo is probably the solution. But a boost leak is possible too, and until you can read codes, you won't see the clues.
 
#6 ·
There's got to be some kind of test to check whether or not kts a leak, or turbo etc. I did the wastegate test to see if the wastegate actuator was properly working or not, that's when you put a compressor nozzle on the vacuum line on the wastegate and use about 20 pounds and see if the wastegate moves back and forth. What's throwing me off is the fact that the turbo seems like it works harder once you've warmed up, I know the air gets warmer and all of that makes a difference but with the n75 disconnected, if I'm not wrong shouldn't this Turbo spool a lot more? A buddy of mine is a Volkswagen Tech overseas and told me to disconnect the n75 hose and if it made a difference that would tell me if it was the N75 or not. Initially I want to order this k04 this week I'm just scared to drop the money on that and install it and have all the problems I'm having now, I'm thinking about getting the kit to change everything on the PCV and 2 aluminum, I'm just curious what else could leak on the Boost end? Sorry for the novels I just find it easier to cover all grounds
 
#12 ·
factory intake box is gone is a big question mark in my mind. thats usually the hallmark of a tuner. im worried what else is touched. also the bad ABS module would give you a "STOP BRAKE FAULT" on your read out display, a check engine light, an ABS light, and your BRAKE light would all be flashing on the dash.
 
#13 ·
Abs light, flashing brake light and CEL are all on. And as far as the intake goes, the original intaxe box was crumbling and falling apart, thus far i put a heat shield and a filter in there to atleast help it run better than the other box. Half the top was cracked off. The theory of the air getting hot, maybe true. Just this smorning, by 4200 rpm's i was at 8LBS .. once it warmed up i had to be at 5500 RPMS to get the same if not less boost in a higher gear even. With the N75 hose to wastegate disconnected, you would think with no vacuum to help the wastegate that it would boost higher? This car makes me loopy:hmmm:
 
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