I bought a nice 91.5 1.8t with 89,000 miles on it. The guy spun the timing belt so I got it for an unbelievable $250. The car is nearly immaculate other than road rash on the bumper. I did all of the repairs myself being a mechanic. I got new valves, headgasket set, full timing set, belts water pump thermostat, the plastic egr manifold, and other misc. parts that I went ahead and replaced wince I had it apart anyway. long story short I have yet to be able to get boost. I only get about 1psi. I am getting a little over -16psi vacuum. I just replaced the diverter valve. I thought I might have put it in wrong so I reversed it, clamped the vacuum line to the wastegate actuator and nothing. I spun the turbo by hand and it turns fine with no real noticeable slack. I have done countless throttle body recalibrations to no avail. I don't hear any vaccuum leaks. Any one have any ideas? Can you make the car boost manually? I want to try that because I can't get to the wastegate linkage to check that or I would have checked that too. Also which way does the diverter go on. The reason I ask is that the origial owner superglued the vacuum nipple back on it so I was wondering it he may have put it on backwards and I might have done the same. Thanks to all.

 

the DV line goes to the intake manifold not the wastegate.

wastegate goes to the n75 then from the n75 back to the turbo.

as for the way the DV goes in, heres a pic of my aftermarket DV.

the short end goes into the intercooler pipe. and the long end goes into the turbo inlet hose. so then the vac line nipple should be pointing straight up when its installed.

 

yea you have something leaking. you should be below -20inHg at idle.

 

I wanted to bring this thread back because I'm having pretty much the same problem as the OP. I'm new to Audi's and turbos in particular. Been a long time BMW owner, so I have very vague knowledge about these cars. I recently picked up a Stock 99.5 1.8TQM.

I got around to installing a boost gauge a few days ago and my vacuum #'s are as they should be, 20-25 Hg at idle, no hesitations, no sputtering, no CEL, everything seems to run as it should. However, I'm not getting any boost readings at all, sometimes the gauge gets up to 1 psi on like 3rd gear but that's it. I've never had a turbo car so I don't know what, or if I should hear any kind of turbo whistle or spinning if there's supposed to be. When the car is stopped at idle, and I accelerate to get going, I can hear a soft whine. Sounds kinda like when your power steering fluid is low, so I don't know if this is the turbo or something else.

I first tried moving around the wastegate linkage, and it's stiff and does not move as it should be. I've tried all the suggestions above but it didn't do anything. I have a question about testing for that though, I tried disconnecting the vacuum line between the n75 and the wastegate, are you supposed to leave those lines open to the air? or am I supposed to plug them? I plugged the lines from the wastegate and n75 when I did it. I also tried running it without the n75 at all and I used a T in it's place. I did however leave the n75 plugged in to the electricity so I wouldn't trip a CEL. Is this the correct way to do it?

When I removed the n75, the T part of the module came off the body, but it just seems like it can happen that it's not broken or anything. I don't know what other troubleshooting steps to take from here on so I'd appreciate any help, thanks in advance

 

On a stock K03, you're probably not going to hear anything from the turbo. I know I didn't until I gutted the cat and have a cat back exhaust. Even now, it's very faint, but the wife likes how it whistles (at her she says).

If you have access to a compressor, search for the tennis ball leak test and give it a try to see if you have any leaks. When accelerating, do you "feel" like the turbo kicks in between 2500-3000 RPM? You should be able to feel the car push a little harder as the turbo overcomes the lag. If you can feel it, then it's quite possible you're getting the boost you should have, and the gauge either is defective, or you have it hooked up wrong.

Best of luck...

 

I'm assuming that leaks is not the problem because my vacuum #'s are as good as they should be, and if I did have a leak it would show there.

Or correct me if I'm wrong if there's a difference between a vacuum leak and a boost leak? I'll try it out when I get the chance regardless.

I haven't really noticed any difference in the car pushing more between 2500-3000 rpms, but then again I haven't really concentrated on feeling for it either so I'll look at that more.

 

Quick update, I ended up going to a junkyard and getting an N75 and DV from another car. I know they're used and can also not be working properly, but for $20 it's worth a shot. So I put them in, and now my gauge shows up to 1-2 psi under WOT, as opposed to 0 boost from before. My vacuum #'s are still as they should be, 20-25Hg with no throttle.

I'm gonna do a leak test to see if I can find anything. My question though, can there still be a boost leak even if the vacuum #'s are correct? Or does it all go hand in hand?

Also, when installing the stock DV, I've read that it doesn't matter which position it's installed in but want to make sure this is correct? My original DV was installed in a position where the vacuum tube is pointing to the left if you're looking at the car from the front, so I re-installed in this same way. However I've seen pictures where the DV is installed with the vacuum hose pointing straight up, can anyone clear that up for me to know for sure, thanks

 

I didn't read all the replies, but check your turbo wastegate arm. I had the same problem on my 97 and found out the arm was snapped. That will cause 0 boost and effectively turn your turbo into a brick that is obstructing exhaust flow. I later found out that although it's not very common, it does happen. Good luck.

 

Yeah actually that was the first thing I had checked. I read that the wastegate link should not be able to move when the car is turned off, and that's how it is. So unless I'm misunderstanding something, the wastegate should be ok.

 

vacuum is only produced between the engine and throttle body. so a vacuum leak is only between there.

a boost leak can be anywhere after the turbo. you can have a boost leak without a vacuum leak, but you cant have a vacuum leak without also a boost leak.