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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old May 16th, 2016, 06:43   #1
Friday1
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Join Date: Jan 2003
Location: Toledo
Default No boost

On a trip yesterday my 2003 Jetta TDI Wagon had a top speed of 68 mph. I had it scanned this morning and the results were:
Turbo overboost condition limit exceeded.
Possible culprits are:
Charge air pressure sensor.
Wastegate bypass regulator valve.
Bad turbocharger.
I would think if the turbo was bad, it wouldn't over boost.
Is the charge air pressure sensor in the ECM box with an air pressure line connected to it?
Where is the bypass regulator valve located?
Any suggestions on how to test these two units? Thanks in advance.
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Old May 16th, 2016, 09:31   #2
wonneber
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Join Date: Oct 2011
Location: Monroe, NY, USA
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Quote:
Originally Posted by Friday1 View Post
On a trip yesterday my 2003 Jetta TDI Wagon had a top speed of 68 mph. I had it scanned this morning and the results were:
Turbo overboost condition limit exceeded.
Possible culprits are:
Charge air pressure sensor.
Wastegate bypass regulator valve.
Bad turbocharger.
I would think if the turbo was bad, it wouldn't over boost.
Is the charge air pressure sensor in the ECM box with an air pressure line connected to it?
Where is the bypass regulator valve located?
Any suggestions on how to test these two units? Thanks in advance.
There are a lot of things that can cause the over boost.
Clogged intake manifold, bad boost sensor (in the intercooler), sticking actuator (on the turbo) or the vanes sticking, and more.

It gets expensive guessing at what to try.

Do a search here for 'over boost' or variations. There is a good one but I do not have the link for it.

Rich W.
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Old May 16th, 2016, 17:30   #3
TreasureLife
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Join Date: May 2016
Location: Whitehouse TN
Fuel Economy: 44mpg
Unhappy I'm having same issue

Sounds like the same issue I'm having with my 2002 TDI Jetta Wagon. I just ordered new vacuum lines, figure that's a good place to start. Someone sent me this link which has good info:
http://forums.tdiclub.com/showthread.php?t=409251
I changed out the N75 valve but that did nothing for my situation. I ordered a new check valve and vacuum hose connectors to replace them all when I get my new vacuum hose. Also got new brake booster vacuum line. Ordered stuff yesterday hope to have stuff by next weekend.
Please let me know of anything you find out and I'll do the same. Good luck!
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Old May 16th, 2016, 18:37   #4
fruitcakesa
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Join Date: Feb 2007
Location: Vermont
Fuel Economy: 40's
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I am dealing with an over boost in my 02.
After replacing all the old vac lines, I tested the turbo actuator with mity-vac and got minimal movement from the turbo lever.
Removed the actuator and tested it out of the car and it worked fine and held vacuum.
With the actuator removed, the turbo lever still had minimal movement.
Stuck turbo vanes is my problem.
Turbo is now off the car and awaiting dismantling and cleaning.
__________________
2004 Jetta TDI wagon 5 speed 278k+ VNT 17 Kerma tune. new heater core
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Old May 16th, 2016, 19:44   #5
Friday1
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Location: Toledo
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Quote:
Originally Posted by TreasureLife View Post
Sounds like the same issue I'm having with my 2002 TDI Jetta Wagon. I just ordered new vacuum lines, figure that's a good place to start. Someone sent me this link which has good info:
http://forums.tdiclub.com/showthread.php?t=409251
I changed out the N75 valve but that did nothing for my situation. I ordered a new check valve and vacuum hose connectors to replace them all when I get my new vacuum hose. Also got new brake booster vacuum line. Ordered stuff yesterday hope to have stuff by next weekend.
Please let me know of anything you find out and I'll do the same. Good luck!
Will do, and thanks for the info. I have been scouring the forum and looking at Youtube vids. Will get under the hood tomorrow. The Youtubes are great and good info. The forum is sometimes hard to follow.
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Old May 16th, 2016, 19:49   #6
Friday1
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Join Date: Jan 2003
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Quote:
Originally Posted by fruitcakesa View Post
I am dealing with an over boost in my 02.
After replacing all the old vac lines, I tested the turbo actuator with mity-vac and got minimal movement from the turbo lever.
Removed the actuator and tested it out of the car and it worked fine and held vacuum.
With the actuator removed, the turbo lever still had minimal movement.
Stuck turbo vanes is my problem.
Turbo is now off the car and awaiting dismantling and cleaning.
Watching a Youtube today there is one showing how to free up the turbo vanes without removing the turbo using spray oven cleaner. That should work if they are not stuck too badly. I don't baby mine much but still could be stuck. Will work on it tomorrow. Thanks and I will post my solution when it is fixed. Bought this car new in 2003 and this is the first time it has given me any trouble.
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Old May 17th, 2016, 10:01   #7
wonneber
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Location: Monroe, NY, USA
Default Vacuum pump fitting

Quote:
Originally Posted by TreasureLife View Post
I ordered a new check valve and vacuum hose connectors to replace them all when I get my new vacuum hose. Also got new brake booster vacuum line. Ordered stuff yesterday hope to have stuff by next weekend.
Please let me know of anything you find out and I'll do the same. Good luck!
Before you take the brake booster line off see if the fitting is loose going into the vacuum pump. (Mine is)
Others have posted about fixing it with epoxy of peening it with a punch.
I may try the epoxy method when I do my timing belt later this year.
I was hoping to find a bad one to take apart to see if the hole could be drilled & tapped for a real pipe fitting.

Rich W.
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Old May 17th, 2016, 10:13   #8
BobnOH
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Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
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Quote:
Originally Posted by fruitcakesa View Post
....................
Turbo is now off the car and awaiting dismantling and cleaning.
I'm asking a question here, because I don't know- Wouldn't it be better to clean the turbo vanes without disassembly?
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Old May 17th, 2016, 12:25   #9
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It took 2 oven cleaner sessions on my turbo to get rid of the overboost and limp mode, but it works.
__________________
-2003 Jetta TDI GLS Manual (Mods: SBC II Daily, .681 5th, VNT17 & PP520, Self Tuned)
-BMW 328is Manual (heavily modded 220whp, track toy)
-BMW Z3 Roadster (Fun in the sun car)
-BMW Z3 M Coupe (1 of 36)
-BMW 328d wagon (Self tuned ~230hp)
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Old May 17th, 2016, 14:05   #10
Nevada_TDI
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Location: Reno, sort of...
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Without knowing which brand of oven cleaner you are referring to, some of them have flammable propellants which is held in the bubbles. If the bubbles have not all dissipated there is a chance the "fumes" will get into the intake causing runaway. If you have a couple of hours you may get the vanes loose, just don't be in a hurry to restart it. Since yours is a 5 speed, if it does anything funny stand on brake and let out clutch to stall engine after turning off key.
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Old May 17th, 2016, 14:50   #11
Friday1
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Good idea, I have had two Detroit diesels runaway on me from governor problems. They were both automatics and it is hard to stop them.
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Old May 17th, 2016, 15:38   #12
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I was spraying into the exhaust end of it, removing the downpipe and filling it up with the foam. Then hosed it down with water. Doubt it would make it into the intake too much.
__________________
-2003 Jetta TDI GLS Manual (Mods: SBC II Daily, .681 5th, VNT17 & PP520, Self Tuned)
-BMW 328is Manual (heavily modded 220whp, track toy)
-BMW Z3 Roadster (Fun in the sun car)
-BMW Z3 M Coupe (1 of 36)
-BMW 328d wagon (Self tuned ~230hp)
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Old May 17th, 2016, 17:05   #13
fruitcakesa
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Join Date: Feb 2007
Location: Vermont
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Quote:
Originally Posted by BobnOH View Post
I'm asking a question here, because I don't know- Wouldn't it be better to clean the turbo vanes without disassembly?
I wanted to do it this way, to learn how to remove all these blasted parts when I ultimately have to do this again , and I feel I can do a much better cleaning on the bench than in the car.
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2004 Jetta TDI wagon 5 speed 278k+ VNT 17 Kerma tune. new heater core
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Old May 17th, 2016, 19:02   #14
TreasureLife
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Join Date: May 2016
Location: Whitehouse TN
Fuel Economy: 44mpg
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Done some reading on using oven cleaner and sounds pretty convincing! Sounds like some people remove exhaust from underneath and some through the exhaust down pipe (seam like this would be easier). I read one article where a guy sprayed thru EGR and says worked great as well ( http://www.myturbodiesel.com/threads...n.17883/page-2 ). Seems like thru EGR be risky. Thoughts?
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Old May 19th, 2016, 10:32   #15
wonneber
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Default Risky

Quote:
Originally Posted by TreasureLife View Post
Done some reading on using oven cleaner and sounds pretty convincing! Sounds like some people remove exhaust from underneath and some through the exhaust down pipe (seam like this would be easier). I read one article where a guy sprayed thru EGR and says worked great as well ( http://www.myturbodiesel.com/threads...n.17883/page-2 ). Seems like thru EGR be risky. Thoughts?
To much spray in the intake could cause a minor contact issue in the combustion chamber.

Just my 2 cents (US)
Rich W.
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