Help Diagnosing Boost Spike

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
I'm getting a significant boost spike and would like some help figuring out what might be causing it.



This is a log of group 11.

Vehicle is a converted auto, so it has an 11mm pump. Nozzles are DLC1019 set up by drivibiwire. I have pulled the VNT actuator off and cleaned it out, actually had little rocks stuck in it. It now moves smoothly. The VNT lever moves loose as a goose. There is no binding or sticking at all. All vacuum lines have been replaced.

The log is from 1500 rpm WOT to about 4000ish rpm.

What could be causing the boost to spike so high? What else can I check. Trying to get the boost spike under control so I can proceed with getting it tuned by Malone Tuning.

Thanks in advance for the help.

Kevin
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
A malfunctioning MAP sensor caused boost spikes in my case. New MAP, no more spikes. This was on the ALH in my Vanagon. Location of the MAP in my case made it easy to change out. I had some "used" sensors to swap in is how I made the discovery.
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
It looks like you don't have enough preload on the acuator and maybe wear to the vane ring.
How much vacuum does it take to pull the vane lever to the stop screw?
 

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
A malfunctioning MAP sensor caused boost spikes in my case. New MAP, no more spikes. This was on the ALH in my Vanagon. Location of the MAP in my case made it easy to change out. I had some "used" sensors to swap in is how I made the discovery.

Is there a way to test a MAP sensor to see if its functioning correctly?
 

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
It looks like you don't have enough preload on the acuator and maybe wear to the vane ring.
How much vacuum does it take to pull the vane lever to the stop screw?
I will check that tomorrow when we get back home. Could the vacuum actuators spring be weak? The vehicle does have 289,000 miles on it.
 

mrfiat

Veteran Member
Joined
Mar 24, 2008
Location
Los Ranchos, NM
TDI
2003 Jetta TDI (Reflex Silver) , 2003 Jetta TDI Wagon (Black)
Have you tried lengthening the actuator rod? That fixed a similar issues for me on two different cars.
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
Is there a way to test a MAP sensor to see if its functioning correctly?
One way is to tap into the charged air pipe or intake manifold and hook up a 0-60psi mechanical gauge to see how it compares to the MAP reading.
 
Last edited:

Owain@malonetuning

Associate Vendor , w/Business number
Joined
Jul 1, 2016
Location
Vancouver
TDI
PD jetta wagon
Stock ECU tuning isn't designed for this much fuel, so that's probably playing a major role there. N75 isn't responding fast enough, you can see it's working overtime up top as well just to keep boost in check.

Definitely working better than it was, I'd add software at this point then make mechanical adjustments from there if needed.
 

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
Stock ECU tuning isn't designed for this much fuel, so that's probably playing a major role there. N75 isn't responding fast enough, you can see it's working overtime up top as well just to keep boost in check.

Definitely working better than it was, I'd add software at this point then make mechanical adjustments from there if needed.
I downloaded and emailed my stock tune to you this morning. Please let me know if you need anything else from me.

Thanks!!

-Kevin Hill
 

mrfiat

Veteran Member
Joined
Mar 24, 2008
Location
Los Ranchos, NM
TDI
2003 Jetta TDI (Reflex Silver) , 2003 Jetta TDI Wagon (Black)
I have the same exact nozzles and pump on my wagon. I did not have the over boost issues that you have. I actually had under boost issues which I partially corrected by shortening the rod.
 

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
I finally got a chance to work on the car again. Hooked up a mitivac to the turbo actuator and the lever begins moving immediately when i start applying vacuum. 1-2 in/hg on the gauge. It hits the stop at around 18 in/hg on the gauge. Do I need to adjust the arm length since it appears to be moving too soon?
 

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI


Just logged another run after loading a stageII tune from Malone. Still having a huge boost spike. I hooked up the vacuum gauge to my vacuum pump to make sure that its working correctly and I get >23 in/hg at idle.

After logging this I noticed that even under deceleration my actual boost is around 150-200 mBar higher than specified. (999 mbar requested/1150ish actual)

Same thing with just driving down the road, the boost is higher than requested. Under light acceleration it follows along with the requested just fine.

Any ideas?
 

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
It looks like you don't have enough preload on the acuator and maybe wear to the vane ring.
How much vacuum does it take to pull the vane lever to the stop screw?
It hits the stop at 18 in/hg. Iit does start moving at about 1-2 in/hg. Pretty much as soon as in squeeze the handle on the mitivac I can see it start to move.

I haven't had any free time to work on the car lately. Hoping to be able to work on it tomorrow. going to try and lengthen the vnt actuator rod.
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
How many miles are on this turbo?
That range of 1-2"hg to 18"hg seems too wide.
Yeah, lengthen the rod and lets see what happens.
The overshoot-undershoot makes me think that there is an area of the vane ring and internal lever that is worn enough so that it does not have precise control over the vanes.

You can see wear in the pocket on this vane ring where the internal actuator lever mates to it. When you mirror that to the wear on the lever, you wind up with a lot of slop and lack of control.
 
Last edited:

Hakcobra

Well-known member
Joined
Aug 1, 2009
Location
Tri-Cities, WA
TDI
2003 Jetta Wagon TDI
How many miles are on this turbo?
That range of 1-2"hg to 18"hg seems too wide.
Yeah, lengthen the rod and lets see what happens.
The overshoot-undershoot makes me think that there is an area of the vane ring and internal lever that is worn enough so that it does not have precise control over the vanes.

You can see wear in the pocket on this vane ring where the internal actuator lever mates to it. When you mirror that to the wear on the lever, you wind up with a lot of slop and lack of control.

293,xxx miles. With the actuator disconnected the VNT lever is very loose. There is no resistance to moving it. Sounds like it might be too worn out?
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
I could be that the lever is not doing much for part of the stroke.
The wear would be more likely on a turbo with a vane assembly that was getting sticky but, at your mileage, it is very possible.
I've taken a turbo apart to find that the worn slot in the picture was almost worn thru to the oblong slot on the right.
You might have to take it apart to be sure.
 
Last edited:

Rrusse11

Veteran Member
Joined
Jan 23, 2014
Location
PA Deutsch Country
TDI
2002 Golf, 5spd; 05 Jeep CRD
"It looks like you don't have enough preload on the acuator and maybe wear to the vane ring.
How much vacuum does it take to pull the vane lever to the stop screw?"


Just had the same issue, when I got there to adjust, the locknut on the vane acutator was loose. I set mine to 5"hg, lengthening the rod.
I can see the difference on my boost gauge, it's no longer out of control
as it spools up. This was sending me into limp mode when pushed
hard in 4th and 5th.





 
Top