Boost oscilation

Lavek6

Active member
Joined
Jun 15, 2017
Location
Croatia
TDI
Golf IV Golf VI
Golf mk4 99 1.9TDI 81kw VNT turbo

I know there is a lot of threads but there aren't same as my problem so.
Wot jums to 1.4 back to 0.5 than 1.1-0-7 and out of rpm in 3 gear , in 4 smaler oscilation, in 2 i drop to 0.5 at 3200 and no time to recover,
Vnt leaver is 100% free no sticking i tried adjusting actuator to even where it can't touch stop screw and still same if it is 18 in/hg or 15/in/hg at stop maybe a 0,1 bar diffrence.
Could it be bad n75 or maybe somenthing with signal to n75 or else?
 

UhOh

Top Post Dawg
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Dec 24, 2014
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PNW
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2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
Yes and yes.

Really need to run some VCDS logs to know for sure. BUT, if it's got the N18 valve (EGR valve) you might try swapping it with the N75 (they're the same).

This could also be attributable to a bad/misbehaving MAF.
 

Lavek6

Active member
Joined
Jun 15, 2017
Location
Croatia
TDI
Golf IV Golf VI
Yes and yes.

Really need to run some VCDS logs to know for sure. BUT, if it's got the N18 valve (EGR valve) you might try swapping it with the N75 (they're the same).

This could also be attributable to a bad/misbehaving MAF.
Today i adjusted actuator to the max lenght only one turn screwed 25 in/hg can't even touch stop screw for 2 mm and car is boosting 1.0 0.7 0.9 2 gear uphill, ***?
 

Dave_D

Veteran Member
Joined
Jun 9, 2003
Location
Gaithersburg, MD, USA
TDI
2015 Passat Titanium Beige six speed manual & Jetta, 1999.5, Tornado Red
Golf mk4 99 1.9TDI 81kw VNT turbo

I know there is a lot of threads but there aren't same as my problem so.
Wot jums to 1.4 back to 0.5 than 1.1-0-7 and out of rpm in 3 gear , in 4 smaler oscilation, in 2 i drop to 0.5 at 3200 and no time to recover,
Vnt leaver is 100% free no sticking i tried adjusting actuator to even where it can't touch stop screw and still same if it is 18 in/hg or 15/in/hg at stop maybe a 0,1 bar diffrence.
Could it be bad n75 or maybe somenthing with signal to n75 or else?
I saw similar behaviour when my intake was clogged, so check that as well.

Dave
 

Lavek6

Active member
Joined
Jun 15, 2017
Location
Croatia
TDI
Golf IV Golf VI
I had biger road from other actuator and put it on because i extended original maximum and it still wasn't enough so adjusted this one that at 18 in /hg it is a bit more than half way from start to stop screw and now it is boosting almoust normal in 2 gear uphill , i will try tomorow on way to work log 3,4 gear boost.
Is this n75 or could it be sometnig with turbo vanes wrong, actuator ? i searched forums and never saw problem like this.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
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2001 Jetta TDI
I agree with you Lavek6, your situation isn't all that uncommon, but your resolution is; you definitely want to dig a bit deeper.
 

Lavek6

Active member
Joined
Jun 15, 2017
Location
Croatia
TDI
Golf IV Golf VI
I agree with you Lavek6, your situation isn't all that uncommon, but your resolution is; you definitely want to dig a bit deeper.
n75 switched for n18 same thing, adjusted actuator back do factory setting in 2 gear uphill instantly boost jumps to 1.3 and down to 0.6 and start to climb again but out of rev, in 4 gear uphill 80 km/h with about stedy 70,80% throttle i can hold boost at 0.9,1.0 if i wot it starts to overboost evrything is ok no sticky vanes actuator moves good with hand pump n75 ok, no vacuum leaks only thing that could be wrong is signal on n75 from ECU but how can i test that?
 

BobnOH

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May 29, 2004
Location
central Ohio
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New Beetle 2003 manual
I guess your actuator adjusts different. On the ALH you adjust it to start moving at 3.5 to 5.0 "/Hg. You can check the full open reading, but there is just the one adjustment.
 

Lavek6

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Jun 15, 2017
Location
Croatia
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Golf IV Golf VI
I guess your actuator adjusts different. On the ALH you adjust it to start moving at 3.5 to 5.0 "/Hg. You can check the full open reading, but there is just the one adjustment.
How cam you adjust start moving ?, i think actuator might be problem because it is not original but from another car because original failed and previus owner got this one which is same as original in evrything except original is much wider so maybe spring inside is not as strong anymore because it was already used, i first thought about this but why did it work ok untill recently
 
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BobnOH

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May 29, 2004
Location
central Ohio
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New Beetle 2003 manual
Car off, connect a vacuum hand pump with gauge direct to the actuator. As you pump note where the arm begins to move.
 

Lavek6

Active member
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Jun 15, 2017
Location
Croatia
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Golf IV Golf VI
Car off, connect a vacuum hand pump with gauge direct to the actuator. As you pump note where the arm begins to move.
i know that but you can't adjust that you can only see if it is ok
Update:
https://ibb.co/kGFepc 5 in/hg still 5.5 in/hg first move, maybe it is not relevant but is 22 in/hg out of N75 normal for idle
 
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Lavek6

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Croatia
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Golf IV Golf VI
Hmmm, I must be out of line, not knowing your set-up. On mine you would adjust the rod with the double nut.
Yes, but how does that change when it start moving the actuator, it will always start to move at 5 "/hg it does not mater where the rod is, or am i wrong?
 
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jimbote

Certified Volkswagen Nut
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Jul 10, 2006
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spiral arm, milky way (aka central NC)
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Tacoma 4x4 converted to TDI
Yes, but how does that change when it start moving the actuator, it will always start to move at 5 "/hg it does not mater where the rod is, or am i wrong?
longer rod=more vacuum required to move vnt ... shorter rod=less vacuum to move vnt ... if you take time to play with the adjustment you'll see how it changes the vacuum range
 

Lavek6

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Croatia
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Golf IV Golf VI
longer rod=more vacuum required to move vnt ... shorter rod=less vacuum to move vnt ... if you take time to play with the adjustment you'll see how it changes the vacuum range
oh i didn't realize until now that road is pushed in already by leaver :) so if it is more pushed already more vacuum will later push it :) so 5 in/hg 18 in /hg is now if i go shorter for 3,4 in/hg i have even more overboost to 1.5 bar,
I really don't know what to try next :(
 

BobnOH

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central Ohio
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New Beetle 2003 manual
So it's set correctly. Only other thing to check is if it moves all the way when you start the car, it's working and the N75 functions.
An engine code would give a clue.
 

Lavek6

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Croatia
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Golf IV Golf VI
So it's set correctlyLH Only other thing to check is if it moves all the way when you start the car, it's working and the N75 functions.
An engine code would give a clue.
Yes it is at stop screw, can it be the signal to n75 or something,it is strange that in 3 gear uphil i get 1.4 - 0.6 - 1.1 - 0.7 and out of revs but if i adjust arm for longest possibel it still overboosts in 2 gear uphil
 

Lavek6

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Croatia
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Golf IV Golf VI
Yes it is at stop screw, can it be the signal to n75 or something,it is strange that in 3 gear uphil i get 1.4 - 0.6 - 1.1 - 0.7 and out of revs but if i adjust arm for longest possibel it still overboosts in 2 gear uphil
Tomorow i will put T on vacum and vacuum gauge between n 75 and actuator so i can see how much vacuum is n75 sending
 

BobnOH

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May 29, 2004
Location
central Ohio
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New Beetle 2003 manual
When the car is off the turbo vanes are wide open. When you start the engine they close. Which means, I guess, the N75 applies low vacuum at full throttle and full vacuum at idle. This seems counter intuitive to some.
 

Lavek6

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Golf IV Golf VI

BobnOH

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central Ohio
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New Beetle 2003 manual
Is that a vacuum gauge (1st video) and what is it connected to? I'm interweb guessing it's showing engine vacuum, which could fluctuate like that.
The 2nd video shows boost falling as you accelerate, which does not seem right
 

Lavek6

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Croatia
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Golf IV Golf VI
Is that a vacuum gauge (1st video) and what is it connected to? I'm interweb guessing it's showing engine vacuum, which could fluctuate like that.
The 2nd video shows boost falling as you accelerate, which does not seem right
1 video yes boost gauge on vacuum lines, it is connected between n75 and vnt actuator so it is vacuum that is applied and controls the actuator.
2 boost is falling because it overboosts and then ecu is overcorrecting and boost drops is my guess, that is why vacuum from n75 flactuates in 1 video
 
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Lavek6

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Golf IV Golf VI
1 video yes boost gauge on vacuum lines, it is connected between n75 and vnt actuator so it is vacuum that is applied and controls the actuator.
2 boost is falling because it overboosts and then ecu is overcorrecting and boost drops is my guess, that is why vacuum from n75 flactuates in 1 video
I think i might find a problem but nor sure, leaver on which actuator is conected has some free play maybe 1 mm but not the way actuator pulls it is left right free play https://ibb.co/fsv5Hx like i drawn in picture and if i tighten screw on road without holding the road so it is tilted and puling the leaver to side more boost deviation are not so big when it is seted to 18 in/hg
I know the adjusment is very sensitive but it is not that big of a play or maybe it is?
 

Nevada_TDI

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2001 Jetta TDI
I don't know how likely, but it is possible the "knob" on the lever inside of the turbo housing is moving around in-and-out of the recess it fits in due to carbon or some other thing. The actuator arm should not move "left and right" but only forward and backward so-to-speak. If it were me I would take the turbo apart and find out why the actuator arm is moving around so much. It is also possible the sleeve/bearing the turbo arm goes through is wallowed out allowing so much play in the actuator arm.
 

Lavek6

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Jun 15, 2017
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Croatia
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Golf IV Golf VI
I don't know how likely, but it is possible the "knob" on the lever inside of the turbo housing is moving around in-and-out of the recess it fits in due to carbon or some other thing. The actuator arm should not move "left and right" but only forward and backward so-to-speak. If it were me I would take the turbo apart and find out why the actuator arm is moving around so much. It is also possible the sleeve/bearing the turbo arm goes through is wallowed out allowing so much play in the actuator arm.
Yea it does look like it is worn out a bit in that hole knob goes trough to vanes, i managed to tigthen road with some diy on lever so it hold's it beteer and i am boosting now 1.1 and holds 0.9, 0.8 sometimes in 3rd gear 4th is 0.9 but 2nd gear uphill stil 1.2 0.7 but start to rise very quick back to 0.9 and car now fill's much better, unfortunately i don't have time to take off the turbo so for now it will have to do :) i really like the car and it is very reliable for 75 km evry day about 25k year but that turbo and fron disc brakes makes me want to sell it,
I changed them last year in November because of strong vibrations and now it is already shaking like crazy downhill braking specialy, what could make them deforme so fast twice ? it is obviusly problem with something else since the disc i changed in November was changed about 16 mounts ago just before i bought the car.
 

BobnOH

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May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Call me dense, but I still don't get what those numbers are (0.0, 0.8...).
Are they inches of mercury in the line from the N75 to the turbo?
 

Nevada_TDI

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Joined
Aug 17, 2008
Location
Reno, sort of...
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2001 Jetta TDI
As far as brake wobble goes did you use cheap-o discs or OEM quality? If the boost problem is mostly settled down but still happens occasionally, you might try a boost controller aka a "Dawes Device" less than $10 USD on eBay.
 
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