Boost issues

79TA7.6

Veteran Member
Joined
May 8, 2006
Location
Live: Wilbur/Creston; Work: Moses Lake Washington
TDI
2003 Jetta GLS 5 Speed
I have been fighting weird boost issues in my 2003 5 speed alh for a little while now. I was thinking it might have been that my timing was starting to walk a little, but this last weekend I replaced my timing belt, 3rd time since I have owned this car, and used all the proper tools and followed the pdf how to. After the timing belt change and getting the timing set properly, the issue seems to be worse. I drive my car nearly 150 miles per day. My 75 mile drive to work this morning was terrible with no power. Once I got to work I messed with a couple of things, IQ set to around 3 or so, but still have no power. I decided to watch my boost on VCDS, and at WOT I am getting a requested boost of 2200 mBar, but only getting 1900 mBar. 300 mBar difference is a little more than 4psi, which is a huge difference. My car does not go into limp mode and is not throwing any codes. Every once in a while I would see the boost spike to 2300, but not very often.

I replaced the stock turbo with a VNT17 and am running a Malone stage 3 tune. With the stage 3 I also deleted the EGR and everything that went with it, including those sensors and valve. Being that the issue got worse after the timing belt tells me I either I know a lot less than I thought as I don’t think the timing belt can effect boost, at least not as much as I am seeing, or that I might have something disconnected. I have gone over all of the vacuum lines and all seems good and I cannot find anything that is unhooked sensor wise.

I do have a mighty vac, but I do not trust the gauge. This was a hand me down and it is in rough shape. I mostly use it to be sure the vanes move, which they do smoothly, and for changing fuel filters. I also have VCDS for doing any type of diagnostics. I just don’t know why to look for or what logs to log.

Anyone have a starting point for me? It feels like this winter when I plugged up the air intake with snow, but that is all nice and clear. Back then I was getting limp mode real bad though.
 

watchingcrow

Active member
Joined
Sep 19, 2016
Location
San Francisco CA
TDI
2003 VW Jetta
Possible Intake Carbon Build (HELP PLEASE)

A long time member trying to guide me with Overboost asked if i had checked for Carbon Build up on my Intake Manifold. I started to do that and got stymied after getting to the EGR, I took off the Hose connected to that and saw inside that EGR, that little Flange Flapper thing moves freely and there is only a light coating of a black oil like substance on the inside surface. To go further is going to take some really manic work - WHICH I AM GLAD TO DO IF THAT IS WHAT I MUST.
The question is: If the inside of the EGR is free of Carbon, doesn't that indicate that the manifold is also likely to be clean?

Thoughts please, please help.

Michael Patrick:confused:
 

flee

Veteran Member
Joined
Sep 19, 2011
Location
Chatsworth, CA
TDI
2002 Jetta GLS wagon
Crow, you already posted this question elsewhere.

79TA7.6, probably limp mode so check out Canadian_Grizzly's limp mode thread.
One easy to do check is to unplug the MAF and see if it improves things.
 

79TA7.6

Veteran Member
Joined
May 8, 2006
Location
Live: Wilbur/Creston; Work: Moses Lake Washington
TDI
2003 Jetta GLS 5 Speed
I was kind of thinking limp mode, but all the times I have had limp mode I have power for a little bit until I either over or under boost. As well, I still have boost, just not what the car is asking for. Again, all my experiences with limp mode the turbo just flat stops producing boost. I will read through the thread to see if I can find new info though.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Limp mode and low power (what you have) are much the same thing and share pretty much the same diagnosis. Keep it simple, diagnose one component at a time, you'll find it.
This could help.
 

boertje

Veteran Member
Joined
May 24, 2002
Location
Coeur d'Alene, ID
TDI
'01, '01, '03 - TDIs all.
On my 2000 golf I battled low power for a time. First I found was sticking turbo vanes. Cleaned those but little improvement. Looking at the boost graph, I was simply not getting actual to meet requested boost. On a whim I checked my vacuum pump. Only 14” Hg! Nipple was leaking. Fixed that and still no noticeable improvement on the boost. Pulled the n75 out of my bug and put that in the golf. Bingo! I guess these things can go bad.
 

79TA7.6

Veteran Member
Joined
May 8, 2006
Location
Live: Wilbur/Creston; Work: Moses Lake Washington
TDI
2003 Jetta GLS 5 Speed
So I ran from work to home and back to work again with the MAF unhooked. Honestly forgot to hook it back up when I got home and it was dark as all get out this morning. Very very little difference. I noticed two things, one was that any and all boost spikes were gone, the other was that from an idle in neutral the engine would rev much easier and faster with it unhooked. What would cause that? I first noticed it because I am having shifting issues and have to rev match. Was having issues after the TB change prior to unhooking the MAF. When I hooked it back up after work it would not rev as fast, easy. I replaced the MAF sensor once, but do not remember when. I have done a lot to this car in the 235k miles I have driven it. Does it sound like this might be going out again?

My first thought was that the canes might be carbonned up, but the actuator moved with zero jitter. My hose coming out of the vacuum pump moves easily, but I am not sure if that is normal or not. I replaced all of the vacuum lines at my last TB change. Is there a way to test the N75 valve? Would hate to drop $50 on something that is fine. Still need to read through the link you posted as well.
 

boertje

Veteran Member
Joined
May 24, 2002
Location
Coeur d'Alene, ID
TDI
'01, '01, '03 - TDIs all.
You can temporarily use the n18 valve used for the asv to test that. If you were close to coeur d’Alene I have a spare on the shelf. Also have a spare MAF.
What kind of vacuum are you seeing? The nipple on the vacuum pump can work loose over time to the extent that you developed a major leak. My 2000 golf was so bad I was only getting 14” Hg. I Re swedged the nipple and it was back up to 25” Hg. Curious what VCDS shows on a graph of requested vs actual boost?
 
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79TA7.6

Veteran Member
Joined
May 8, 2006
Location
Live: Wilbur/Creston; Work: Moses Lake Washington
TDI
2003 Jetta GLS 5 Speed
Requested was reading 2300 while actual was only hitting 1900. I am going to try to see if I can find a vacuum gauge before I leave Moses Lake, as well as possibly a new mighty vac. I have removed all of my EGR as well as my ASV, in doing so I removed all my valves. This was 150k ago and I have no idea where they are, I might have been dumb enough to sold them. Unfortuanately I never drive my car east, it always heads west for work these days. I appreciate the offer though.
 

79TA7.6

Veteran Member
Joined
May 8, 2006
Location
Live: Wilbur/Creston; Work: Moses Lake Washington
TDI
2003 Jetta GLS 5 Speed
So I wanted to let everyone know that I figured out what the issue was. Turns out that my MAF sensor was dirty. I bought some MAF cleaner and sprayed the crap out of it. I got all of my power back. I am thinking it had been dirty for quite some time. I started to notice a power loss since mid winter when I was driving in some very wet snow, wet enough that it clogged my snow screen.

I will have to keep an eye out for poet in case it starts to drop off again. I am not sure how well or how long the cleaner stuff works. I figured I was jotmiut anything, and it sure beat buying a new sensor.
 

79TA7.6

Veteran Member
Joined
May 8, 2006
Location
Live: Wilbur/Creston; Work: Moses Lake Washington
TDI
2003 Jetta GLS 5 Speed
So my power started dropping off again last week. Figure I got about 10k out of the last cleaning. I just cleaned it again today. Won’t drive it till Monday to see if it comes out of it. Think I am going to have Malone retune as I installed a VNT17 turbo and am going to upgrade the MAP. Figure I will ask him about deleting the MAF this time.
 

maxmoo

Veteran Member
Joined
Jan 19, 2011
Location
Lakefield, Ontario, Canada
TDI
2000 golf, 2001 golf, 2000 beetle, 2003 wagon, 2004 golf, 2004 jetta, all diesels
These MAF's don't really 'clean' well. Better to replace it when it is failing.
This has been my experience too.
Clean it and if it helps it usually starts acting up again in a couple months....replace it with a genuine unit and full power is restored for years.
 
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