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N75 or Turbo Vanes

maxcars1

Full Member
Nov 9, 2004
735
0
Recently, my car went into I believe limp Mode or boost spiking what ever Mike called it at Jabba. This was noticed when I was doing more than the legal limit up a long incline stretch on the A1. The car just felt like it hit a brick wall - the car was under load clearly. It was that bad I had to pull into the inside lane. When I came of the A1 and into a 30mph limit it seem OK. Further, after restating she was fine, so I took it back to Mike at Jabba and wound back the bhp by 7bhp. I thought this was sorted, but like I said I dont drive her everyday. I came back down the A1 on the way back from work up the same long hill, I was doing about 80mph in top before i started to climb then it felt like there was nothing there, as if it need time to spool up. Now doing 80mph would mean the turbo was on boost surely. I've since spoken to Mike again, who said he would take it back and put it on the other rollers to produce load.

Been with Mike today at Jabba, the turbos running away, he's never seen anything like it - not only in remap but standard At a certain point it just shuts down, is guttess either under load or feeding the power in. He said its probably one of the above. I'm going for the
N75 first and we've agreed with the local VW dealer that I'll have to pay a handling charge of £33 if I want to return the valve - quoted £110 for the part ish. Worst case is sticking vanes, bloody turbos but again I hope not as just run out of warranty (only don 45k with FSH) and after the recent hassle with "goodwill" requests with SEAT UK I'm not holding my breath. What do you guys think? Mike's ruled out the MAF.
 

maxcars1

Full Member
Nov 9, 2004
735
0
Jon TDI said:
Definately sounds like an over-boosting problem. This would trigger the ECU into "limp" mode.

The N75 controls the boost limitation, so that's a good starting point.


Thanks Jon - I really hope so; it's the cheaper option. I've been doing a bit more reading about this N75 now. Is it combind with the N18 EGR valve? the box of pipes across the drivers side strut top mount. I also heared that you can check the operation under Block 11 of VAGCOM to see if the valve will click in and out. Also you can check the VNT diaphram linkage to see if its moving the vanes. It seems to me that these basic checks haven't been done and that the simple method is change a component or ellimination - However the part is an expensive ellimation at £110. Any thoughts on this?
 

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
I think it's all combined in one unit on the Mk4s - the black box on top of the driver's side suspension strut with numerous vacuum pipes attached...?
 

Ant FR

Full Member
Feb 15, 2005
2,861
0
Kent
get a bigger intercooler.

Mine was always doing this, and going into limp mode.

Changed the intercooler for a FMIC of fth ecupra and never ever done it since. Touch wood.

The standard intercooler on the mk4 is just shite, shite in location, shite in size, get rid and enjoy th eincrease in reliabilty.

When i took mine to Le mans this year even in 38c heat it stilll pulled lovely and no limp mode at all.
 

maxcars1

Full Member
Nov 9, 2004
735
0
If only my bank balance was as big as yours Ant Fr and my wife was more understanding oh and I didn't have two teenage daughters
 

maxcars1

Full Member
Nov 9, 2004
735
0
Well I spent all afternoon at Jabba and the car still isnt fixed:mad: Slaved in a new solinoid (the one on top of the drivers strut) and still the same. As standard she still runs away with the boost and then drops out, so I'm running back as standard at the mo until the fault is cured. Mike is lost and has checked the wastgate all the vacume pipes down to the vacume pump at the side of the head. Everything moves as it should etc. The expense of the turbo is not an option at the moment if the game is ellimination - if only I had a bottomlesss pit of money. And there's no point in taking it to the stealers as they wont be able reproduce the fault at normal speed limits. If they could I would, and then go for a Goodwill request, seeing as its only done 42k. Any techies had this problem?
 

Angusrob

Full Member
Jan 11, 2005
129
0
Tayside
maxcars1: So what was the outcome here Angus?

First of all seat refused to acknowledge a turbo issue. Then after running out of options told the dealer to strip and rebuild the turbo. The garage decided just to replace it.
There has been no fault since, however think I got used to it having more power when it was over boosting (is this correct). Feels slow now compared to before, better in this cold weather though than the summer.
 

dmjw01

Upstanding Member
Jul 28, 2005
442
0
Woking, UK
www.dmjwilliams.co.uk
I read a thread by a person on TDIClub who managed to free up the VNT mechanism on his turbo by going into Basic Settings of Group 11 in VAG-COM. Apparently, this causes the ECU to cycle the VNT mechanism back and forth continuously between zero and full boost. The thread is here.

Presumably you have to do this with the engine switched on (otherwise no vacuum) and at idle.

Has anyone done this? I haven't seen or read anything else about this apart from that one thread, so I can't vouch for whether it's a good thing to do or not.
 

maxcars1

Full Member
Nov 9, 2004
735
0
dmjw01 said:
I read a thread by a person on TDIClub who managed to free up the VNT mechanism on his turbo by going into Basic Settings of Group 11 in VAG-COM. Apparently, this causes the ECU to cycle the VNT mechanism back and forth continuously between zero and full boost. The thread is here.

Presumably you have to do this with the engine switched on (otherwise no vacuum) and at idle.

Has anyone done this? I haven't seen or read anything else about this apart from that one thread, so I can't vouch for whether it's a good thing to do or not.

Mike has checked the wastegate linkage and its moving as it should. I suppose I could ask hime to cycle the N75 when its all connected up and see if the linkage moves, but he's disconnected the vacume pipes and they seem ok and a new N75 didn't cure the fault I can't see any benefits of this check really. [:@]
 

techie

Skoda Techie
Mar 22, 2003
5,438
5
Worcs
The only thing I know to cause it other than the N75 is the turbo itself. Cycling the actuator sometimes works.

However my Fabia did do it occasionally, both std and modified. Allways at light throttle whilst cruising at highish speed.

Sadly never did get to the bottom of it.
 

maxcars1

Full Member
Nov 9, 2004
735
0
techie said:
The only thing I know to cause it other than the N75 is the turbo itself. Cycling the actuator sometimes works.

However my Fabia did do it occasionally, both std and modified. Allways at light throttle whilst cruising at highish speed.

Sadly never did get to the bottom of it.

So my options are:

1. Strip turbo and clean - refit manhours could be quite alot
2. Replace the turbo new - lots of money again
3. Be lucky and find a low mileage VNT15 labour to fit needle in a haystack?
4. Get TurboDynamics to providea Hybrid with VNT17 bits same price as a VAG unit?

Bottom line is nobody can defo say this will work

or

5. Sell the car and deny all knowledge, then by a 130pd.
 
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