# Overboost/Wastegate issue



## EmbraceEphemeral (Feb 4, 2012)

Hey, I read all through this forum and didn't see an answer to my question so I thought I would stop lurking and register so I can try to track down the problem I am having. Most everyone on here seems really knowledgable so hopefully someone will have some advice. 

I have a 2001 Audi TT 225hp (AMU) Quattro with 95k. I am the 3rd owner so I do not know what was done to the car before I bought it, but I believe it is all stock. 

I just took the car to the shop because of a CEL. They found several codes and ended up installing a vacuum hose assembly (06A 133 773 A). I also need to replace an O2 sensor (post cat-converter) and I need to replace the thermostat. The car is running cold. 

The problem I am having now is overboost. From what the mechanic told me, when I am merging onto the highway and really get on the gas, the turbo is overboosting and the car notices this and cuts the fuel supply causing the loss of power and a horrible feeling/noise. He took it back to the shop and was able to reach down and pull on the wastegate shaft to get it to move. He noticed a little scraping feeling and then it moved freely. However, that didn't solve the problem. As soon as I drove it of the lot it started doing the same thing. 

Does any of this sound familiar to anyone? 
I dont think it was carbon build up causing it to stick because it started back up immediately. 
I was told you shouldn't be able to move the wastegate shaft by hand? The mechanic said its difficult to do, but he was able to. 
Someone mentioned the wastegate might be out of adjustment? 
Looks like its a new washer, so someone must have had the turbo off recently. Maybe they didn't adjust the wastegate properly? Although it didn't do this in the first week that I bought the car. It just started doing this after they replaced the leaking vacuum hose assembly. 
The mechanic said its possible that the bushings inside the turbo where the wastegate arm connects could be shot? 

Any help would be awesome!!!! 
Thanks! 
Kyle


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## AmIdYfReAk (Nov 8, 2006)

It was common on older turbos for the wastegate assembly to seize or faul up and cause some issues, but yes, the wastegate assembly should move if enough pressure is applied to it by hand or other means. 

Anyway, something I'd like for you to expand on, when your going into limp ( when the boost cuts out and takes the power with it ) you explained a noise as well, what noise is that? 

And is it possible to have a picture of the hose they replaced?


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## EmbraceEphemeral (Feb 4, 2012)

Hey AmIdYfReAk, 

I will get some photos of the vacuum hose assembly they replaced, tomorrow. The hoses are on the upper end of the engine in the front near the dipstick, and they run around the passenger side and across the firewall. They ran a smoke test to detect the leaks. There were all kinds of codes because of these leaks. The car seemed to run fine though. It wasn't doing this limp thing prior to me taking the car in. 

As for the sound, Its really hard to explain and it could just be the sound of the car being starved for fuel and jerking a bit. It wasn't a squeak or metallic sound or anything really distinguishable. I hate to be so vague, but I will have to really listen next time and try to pin point it. 

Is it possibly for a wastegate to function sometimes and not others? Like I mentioned, I haven't driven it much with this condition because I wasn't sure if I was doing damage, but it doesn't always go into limp, sometimes it will wind all the way out and run great. But more often than not it was going limp on the merge ramp of the highway. 

So I will get some photos tomorrow and post them. 
Thanks for your help!


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## Vaughan gti mk4 (Aug 24, 2008)

If you had a boost gauge you could see what is going on a lot more. If you knew what psi the car was was rumning it would help. Wastegate is still good im sure. If you pull hard it should move. My car was overboosting and hitting limp when my MAF and spark plugs were bad. I think the 02 has a big part in this. My brothers 1.8t had bad 02s and it would run ok if you got on it sometimes but others it would over boost really bad and backfire.


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## AmIdYfReAk (Nov 8, 2006)

Another thing to try is go to your local hardware store and get a hard fitting and bypass the n75 ( boost controller on the intake )... Then you should only boost 5psi, no matter how hard you romp on it. 

And I agree with the above poster, a boost gauge tells you so much information.


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## EmbraceEphemeral (Feb 4, 2012)

Here is a photo of the hose assembly that was installed. It was $250, so its a pretty extensive system of hoses I imagine.....or at least I hope! ha There are a few check valves that are part of that assembly also, those are under the intake manifold where the right arrow is pointing. 










I also bought a boost gauge and have the line ran  I made a custom mount for the gauge to go inside the left center vent. Once the epoxy dries I will hook that up and we'll see whats going on. When driving it today I noticed the sound of the DV wasn't consistent. Loud sometimes, quiet other times and a little flutter every now and then. Makes me wonder if its shot.


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## EmbraceEphemeral (Feb 4, 2012)

> My car was overboosting and hitting limp when my MAF and spark plugs were bad. I think the 02 has a big part in this. My brothers 1.8t had bad 02s and it would run ok if you got on it sometimes but others it would over boost really bad and backfire.


 Im going to change my plugs tonight or tomorrow also. I haven't one that yet and I am sure they are fairly old (bought the car used). 
I also think I have a bad O2 sensor somewhere. The shop mentioned seeing a code that was an O2 sensor. I have a slight haunting rev but only occasionally. So that could be part of the problem as well. 

Man.... It seems like there are a million little details that need to be right on key for this car to run right! ha


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## EmbraceEphemeral (Feb 4, 2012)

Very strange......I am not getting a reading on my boost gauge. I can suck and blow on the hose to get the needle to move so I dont think the hose is collapsed, but when spliced into the FRP hose.....nothing. The hoses are of course a little dry looking, so it might not hurt to replace them, but still I think I would get some reading.


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## AmIdYfReAk (Nov 8, 2006)

Follow it down a little and see if it's still plugged in, the port is just under the corner there.


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## viperius (Nov 7, 2008)

when my car had an over-boost problem the N75 was dead. One way to test is to unplug harness plug on the valve.

This will make the car run only on the wastegate which should be no more than 10PSI.


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## [email protected] (Jul 1, 2009)

Another cheap/easy troubleshooting trick is pressurizing the vacuum line running down to the turbo actuator. You can use a small hand pump or bike pump to put ~8psi onto the line. You can then look past the charge pipe to watch for movement at the actuator control rod. If you can get it to go up and down, the turbo isn't your issue. If you CAN'T, make sure it isn't just a tear in that line running down to the actuator.


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## EmbraceEphemeral (Feb 4, 2012)

UPDATE:

I pressurized the line leading from the N75 to the turbo and the actuator control rod freely moved back and forth. Didn't appear to have any issue there so I think the wastegate is functioning. I also put a 12v charge to the N75 and it clicked....I imagine that means it is functioning properly, unless there is an electrical issue causing the N75 to malfunction? 

I did find a problem though. The hose leading from the manifold to the FPR was broken. I fixed this hose and I noticed an improvement in the cars performance. Now it feels like the turbo is actually working to a certain degree. Now my boost gauge is actually getting a reading which also means the FPR should be working now. The boost gauge reads about 8lb vacuum when idling. I will have to drive a bit more, but it doesn't seem like I ever get up to 10lbs of boost.

So the car is running better now, but what it feels like is when I am accelerating quickly I get intermittent boost. Feels a little jerky like its boosting and losing boost then boosting and losing it. How big of a role would a bad diverter valve play in this issue? Its the stock DV. Maybe its shot and only holding a certain amount of pressure then releasing, then building and releasing? Not too sure if that would be the case or not.

What about the N75.....could it be getting a bad signal and getting intermittent power causing it to open and close the wastegate sporadically? 

Either way, It was a step in the right direction by fixing the vac line to the FPR and being able to see what my boost gauge is reading.


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## groggory (Apr 21, 2003)

Do an intake pressure test per my sig


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## AmIdYfReAk (Nov 8, 2006)

I also agree with the test, a stock awp should do roughly 20 inches ( not lbs ) of vac, and 11psi of boost.


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## EmbraceEphemeral (Feb 4, 2012)

Doing an intake pressure test seems to be on the upper end of the DIY spectrum considering my limited tools. I will see about having that done though.

Oh and it was getting 10in (not lbs, sorry) of vacuum when idling and it did get up to 11lbs of boost a few times on the highway. 

I just got back from an hour long trip on the highway. Now at idle it reads close to 20in vac but never boosted over 5lbs. Also, not I am not feeling the turbo really kick in but I do hear it blow off a little. 

Seems like the car never runs the same way twice!

Oh and its the AMU engine if that makes a difference. 2001 225 AMU 6sp with 95k.


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## EmbraceEphemeral (Feb 4, 2012)

Can you suggest a good tutorial on doing the pressure test? Im reading around and it doesn't seem as complex as I first thought.

Thanks!


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## AmIdYfReAk (Nov 8, 2006)

Anyone should be able to understand the lack of tools, most build a rig out of a dog food can and a shrader valve then mooch a small portable compressor off of one of their friends... =D

Anyway, when the car is at temp, in neutral, and nothing's on ( heater and etc ) THEN you should be at 20inches.

During warmup the vac readings can be a little all over the place due to cold start conditions.


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## AmIdYfReAk (Nov 8, 2006)

As per Greg's FAQ/signature.

http://tinyurl.com/pressure-test

http://www.myturbodiesel.com/1000q/multi/boost-leak-tester-DIY-check.htm


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## EmbraceEphemeral (Feb 4, 2012)

Thanks for the links. I just read through the first one and I don't know what I was thinking but that sounds MUCH more simple than I thought. Too bad I don't feed my dogs canned food, looks like I will be stopping at Lowes tomorrow! haha.

This slipped my mind, but I actually need to install a new thermostat. The shop I took my car to said its running about 15c too cold. Sometimes the gauge reads half way between hot and cold, but most of the time its only a 1/4 past cold....if that. I don't think that plays into the issues my car is having, but I need to get that fixed soon so I can get up to normal operating temp.


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## groggory (Apr 21, 2003)

EmbraceEphemeral said:


> Thanks for the links. I just read through the first one and I don't know what I was thinking but that sounds MUCH more simple than I thought. Too bad I don't feed my dogs canned food, looks like I will be stopping at Lowes tomorrow! haha.
> 
> This slipped my mind, but I actually need to install a new thermostat. The shop I took my car to said its running about 15c too cold. Sometimes the gauge reads half way between hot and cold, but most of the time its only a 1/4 past cold....if that. I don't think that plays into the issues my car is having, but I need to get that fixed soon so I can get up to normal operating temp.



Our car actually relies on that temp for some calculations. Get it fixed with a new green top.


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## EmbraceEphemeral (Feb 4, 2012)

Will do.
I was expecting to have to replace the thermostat (standard looking part for all cars), but the coolant temp sensor(green top) should be replaced you think?

P.S. I cant wait for my Bentley Service Manual to show up! Until then, Google! I should be able to figure out where this part is and how to replace it! ha

I really do think that sites like this should have a way to shoot a few bucks to the people who help troubleshoot and eventually solve problems. I definitely appreciate the advice! I have made more progress through advice on here than the shop I took my car to made. European Auto Specialists my ass.


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## groggory (Apr 21, 2003)

EmbraceEphemeral said:


> Will do.
> I was expecting to have to replace the thermostat (standard looking part for all cars), but the coolant temp sensor(green top) should be replaced you think?
> 
> P.S. I cant wait for my Bentley Service Manual to show up! Until then, Google! I should be able to figure out where this part is and how to replace it! ha
> ...


vortex policies don't allow special treatment of anyone. Otherwise I'd say that's a great idea.


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## AmIdYfReAk (Nov 8, 2006)

Cts:
http://forums.vwvortex.com/showthre...rature-sender-with-the-updated-one-(green-top)

Thermostat..

http://forums.audiworld.com/showthread.php?p=16925102


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## EmbraceEphemeral (Feb 4, 2012)

Thanks for the links. I am really anxious to get both the thermostat and temp sensor replaced.....and THEN I will check for leaks. The car is all over the place! Ran bad this morning, then on my way home today it was actually up to the correct operating temp and started to run pretty good from what I could tell! I am getting 20in idling and 11lbs when accelerating....but it is actually spiking up over 20lbs from time to time.

Will update once I replace the thermostat and temp sensor.
Fingers crossed!


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## groggory (Apr 21, 2003)

EmbraceEphemeral said:


> Thanks for the links. I am really anxious to get both the thermostat and temp sensor replaced.....and THEN I will check for leaks. The car is all over the place! Ran bad this morning, then on my way home today it was actually up to the correct operating temp and started to run pretty good from what I could tell! I am getting 20in idling and 11lbs when accelerating....but it is actually spiking up over 20lbs from time to time.
> 
> Will update once I replace the thermostat and temp sensor.
> Fingers crossed!


The 1.8t is fickle with vac leaks. An intake pressure tester is essential equipment for any 1.8t mechanic


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## EmbraceEphemeral (Feb 4, 2012)

Ok, so I have my Intake Pressure tester made. Turned out pretty good! Simple and solid with a pressure gauge in line so I can fine tune the air pressure I am sending through the intake...Now I have a question about quality hose clamps. 
What would be the best style of clamps to get, and moreso what are the sizes I would need to cover a wide range of hoses under the hood? Im sure thats an incredibly ambiguous question since there is a large variety of hoses, but im sure there are a few 'standard' must have sizes that work for most of the boost/vac hoses. I just want to be prepared with the right kind of clamps and quality hose before I start hunting for leaks. I guess I am expecting to find some, but its good stuff to have on hand regardless.

Thanks!!!


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## groggory (Apr 21, 2003)

EmbraceEphemeral said:


> Ok, so I have my Intake Pressure tester made. Turned out pretty good! Simple and solid with a pressure gauge in line so I can fine tune the air pressure I am sending through the intake...Now I have a question about quality hose clamps.
> What would be the best style of clamps to get, and moreso what are the sizes I would need to cover a wide range of hoses under the hood? Im sure thats an incredibly ambiguous question since there is a large variety of hoses, but im sure there are a few 'standard' must have sizes that work for most of the boost/vac hoses. I just want to be prepared with the right kind of clamps and quality hose before I start hunting for leaks. I guess I am expecting to find some, but its good stuff to have on hand regardless.
> 
> Thanks!!!


little tiny hoses can be tackled with small and large zip ties. For a professional install you'll use one use crimp clamp a'la OEM style.

Small'ish hoses can be tackled with 3/8" worm gear hose clamps

Large hoses should be secured with a QUALITY 2 1/2"-2 3/4" worm gear clamp or better yet... an equivelant T-Bolt clamp.

Exact sizes will vary depending on what exactly you're doing.


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## EmbraceEphemeral (Feb 4, 2012)

Sounds good!
I might use the crimp clamps on the easier to get to areas and have some zip ties for the tighter spots. I wasn't sure if the worm gear clamps would be alright to use since they tend to cut into the hose. But I guess I am also thinking about when they are used on motorcycle fuel lines, since the fuel typically softens the rubber. Since these aren't holding fuel and don't need to be torqued down, they should work well. 
Thanks!


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## groggory (Apr 21, 2003)

Only touch hoses that have problems


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## EmbraceEphemeral (Feb 4, 2012)

Well, I just did the intake pressure test and the system seems air tight! Not even a tiny leak! The car is hot right now, so I will test it again once its cold. I was really hoping to hear some air leak so that I could solve the problem.

Its running at a steady 20in vac at idle and will climb up to 11lbs easily but then will typically keep rising all the way up to 21lbs or so and then I guess it goes into limp.

Even though the N75 clicked when I sent power to it.....could it possibly be bad?
Any other thoughts on what it might be? 

When I first bought the car I would notice the turbo really kick in around 2500rpms and now I really don't feel that "pull" ever, its just a steady climb of boost and then overboost. And this problem didn't start until after the shop installed new intake vacuum hoses. I wonder if they could have installed one of the check valves the wrong direction? I know they said it was a series of hoses and valves that they replaced. I am not very pleased with that place, and will never take my car back........they busted my oil dipstick housing and glued it back together......hack shop.


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## groggory (Apr 21, 2003)

EmbraceEphemeral said:


> Well, I just did the intake pressure test and the system seems air tight! Not even a tiny leak! The car is hot right now, so I will test it again once its cold. I was really hoping to hear some air leak so that I could solve the problem.
> 
> Its running at a steady 20in vac at idle and will climb up to 11lbs easily but then will typically keep rising all the way up to 21lbs or so and then I guess it goes into limp.
> 
> ...


I'm wondering about your wastegate operation...

Try this...

Unhook the line from the wastegate to the N75.

Connect this line to shop air w/ regulator set to 0 PSI.

Have a friend slowly increase the shop air pressure and see if the wastegate actuator is slowly moving as you increase pressure.

...

If this moves freely, I'm wondering if the wastegate adjustment screw has been changed from the OEM setting. If the wastegate has been 'cranked' it will cause the wastegate flap to stay closed more (aka give you more boost) for the same N75 duty cycles. You want your wastegate to act as an OEM setup. This is what the software expects.


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## EmbraceEphemeral (Feb 4, 2012)

Hey Groggory, 
I just went around the block with the N75 unhooked and, as I thought, it only boosted up to 5lbs. 

Removing the line from the N75 to the wastegate and hooking air up to it to check the function was one of the first things I did when I got my car back and it was acting up. It appears to be opening and closing smoothly, although I would like to hook up a more sensitive gauge to see exactly how many psi it is taking to open and close. I can see the linkage and it doesn't appear that the nuts have been adjusted to change the throw of the wastegate. The car ran great before taking it to the shop (aside from having leaks that they seem to have fixed) but the shop would have had no reason to adjust this and it doesn't look like they did. 
The guy at the shop did say that he moved the wastegate linkage by hand and it felt like it was hanging up a little but then freed up. It started acting up right away though, so I dont think its carbon. I wonder if the "flap" the wastegate opens and closes it wore and hanging up a bit?
Would rev flare be at all related to this? Or is that a throttle body or clutch sensor issue alone? Getting killer rev flare when accelerating quickly.

Sorry I am all over the place on this thread. I wont break down and take it to the shop until we're all out of ideas! 
Thanks alot!


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## groggory (Apr 21, 2003)

Do you have a vag com? If you do, it would be helpful here to see a graph with

RPM vs. boost req (PSI)/ boost act (PSI)/ n75 duty cycle(%)

...all on a 3rd gear pull 2k-6500


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## EmbraceEphemeral (Feb 4, 2012)

I really wish I did, but unfortunately I do not.
I live in Cincinnati.....maybe I will put an ad out and see if anyone around here might be able to help me out with that.


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## EmbraceEphemeral (Feb 4, 2012)

Got a vag-com cable today (thank you craigslist!) and just downloaded VCDS Lite from Ross Tech. 

I'll mess around with it and see what I can come up with. Hopefully with the Lite version I can graph the "RPM vs. boost req (PSI)/ boost act (PSI)/ n75 duty cycle(%)"


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## AmIdYfReAk (Nov 8, 2006)

Block 115 is boost.. also has RPM


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## EmbraceEphemeral (Feb 4, 2012)

Got the vagcom to work today. Found out that it doesn't like to run on a Mac that is using parallels to operate Windows XP. ha!

I have to play around with it ALOT more, but my next step will be to log a 3rd gear pull and graph the RPM vs. boost req/ boost act/ n75 duty cycle. But here are the fault codes......one of which in particular might be the answer to my main problem:


VCDS-Lite Version: Release 1.1

Tuesday, 21 February 2012, 17:22:10.

　

Chassis Type: 8N - Audi TT

Scan: 01,02,03,08,15,17,22,35,37,45,55,56,76,77

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Address 01: Engine Labels: 06A-906-032-AMU.LBL
Controller: 8N0 906 018 T
Component: 1.8L R4/5VT G 0003
Coding: 06710
Shop #: WSC 01236
VCID: 42F7C90B5D81
6 Faults Found:
17963 - Charge Pressure: Maximum Limit Exceeded
*P1555* - 35-10 - - - Intermittent
17544 - Shareware Version. To Decode all DTCs
*P1136* - 35-10 - Please Register/Activate - Intermittent
17956 - Shareware Version. To Decode all DTCs
*P1548* - 35-10 - Please Register/Activate - Intermittent
16806 - Main Catalyst; Bank 1: Efficiency Below Threshold
*P0422* - 35-10 - - - Intermittent
17832 - Shareware Version. To Decode all DTCs
*P1424* - 35-10 - Please Register/Activate - Intermittent
16795 - Shareware Version. To Decode all DTCs
*P0411* - 35-10 - Please Register/Activate - Intermittent
Readiness: 0000 0000
-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: Redir Fail!
Controller: 8N0 907 379 E
Component: ESP 20 CAN V004
Coding: 18446
Shop #: WSC 01236
VCID: 3E0FBDFB2979
1 Fault Found:
00285 - ABS Wheel Speed Sensor; Front Right (G45)
35-10 - - - Intermittent


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## EmbraceEphemeral (Feb 4, 2012)

I'll look into the P1548 code a little more.....but all the symptoms are pointing to a bad N75 valve OR bad wiring.


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## EmbraceEphemeral (Feb 4, 2012)

Replaced the N75 valve with the "race" valve from ECS. That took care of my overboosting (24psi) and now my max boost is around 14-15psi. A few more lbs than stock.

Still have rev/throttle flare while romping through the gears. It does this 95% of the time but not always. The stock DV is failing so I am expecting a Forge 007 'A-line' diverter valve to show up tomorrow. Not sure if this will fix the rev flare problem or not, but it seems like when it flares I do not hear the 'whoosh' of the dv. So maybe this will help.....could hurt.


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## Jdub337 (Feb 23, 2012)

*I have your same problem*

Just last month i changed all my hoses with silicone pipes including a Turbo inlet pipe. My dv sounds fine but my car no longer has the balls it used to. My crankcase breather hose failed after replacing the other hoses (probably was just on its way out), so i replaced it. My car is Unitronic chipped and i don't know what stage it is. I just know i've looked down at the gauge in the past and it averaged 15psi. Also at times i've seen 18-20psi at hard runs. Thats no longer the case cause i can only read at most on my boost gauge 11psi. I don't know if its a wastegate, n75, or chip software issue.


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## vladub26 (Apr 23, 2011)

*Help! Same problem*

I too am experiencing this overboost bulls**t when trying to quickly accelerate from low rpms. Not only that, but it feels as though i have low oil pressure until my car is warm. The car wants to choke at idle when i hit the gas.
I have an 04 AWP 1.8t, I have replaced my coolant temp sensor, dv (running a forge splitter), recently did 2.5" catback, seafoam and an oil change. 
I have a boost gauge and prior to all this was happily holding 11.6 psi.

Now when I hit boost in low rpms, it just builds boost till i let off the gas or I hit fuel cut @ like 17psi.

I've tried replacing the n75 with one from an 01 a4 1.8t, and the problem remained. He is chipped, idk if that matters?

I've also BYPASSED the n75 completely with an MBC and while this fixes the overboost, this hesitation when i hit the gas at low rpms still remains. 

One last thing.. my injectors are rather noisy, and I have not replaced the fuel pump or fuel filter. I'm at 150k. Dont know if thats relevant but just throwing it out there. SOMEONE PLEASE HELP ME!


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