N75 boost control solenoid

Sayray24

Well-known member
Joined
Apr 5, 2010
Location
Olney, IL
TDI
1998 VW Jetta
how easy/hard/expesive would it be to replace the boost control solenoid on my 1998 jetta? once i get above 2800-3000rpm at 1/2 to full throttle it starts pulsing/surging.
 

bikeprof

Veteran Member
Joined
Sep 2, 2005
Location
Pagosa Springs, Colorado(YEAH!)
TDI
1996 Passat B4 Variant white, 1996 Town & Country 3.8 LXI
Hmmm, sounds like the intake manifold may be clogging up, dirty MAF connector and some hole in one of the intercooler pipes(very small hole, thus higher pressure makes it bleed).

N75's do or don't work...
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Dewey, AZ
TDI
Only the B4V left
Hmmm, sounds like the intake manifold may be clogging up, dirty MAF connector and some hole in one of the intercooler pipes(very small hole, thus higher pressure makes it bleed).
N75's do or don't work...
When I had my RC2+ installed, my N75 was limiting the car to 10.5 lbs of boost. I didn't notice since that's almost stock. A few taps and some cleaning got it a little above that, but only when I swapped a new one on did I get the full 17 lbs requested.

I agree though, it sounds like a different problem is afoot.
 

Sayray24

Well-known member
Joined
Apr 5, 2010
Location
Olney, IL
TDI
1998 VW Jetta
huh ok well i read a post that had the exact same symptoms and they said it was the n75 wearing out.
 

dieseljunkie

Veteran Member
Joined
Dec 29, 2006
Location
New England USA
TDI
96 Passat TDI wagon
how easy/hard/expesive would it be to replace the boost control solenoid on my 1998 jetta? once i get above 2800-3000rpm at 1/2 to full throttle it starts pulsing/surging.
I had the exact symptoms you have. After a lot of testing for pressure leaks and the turbo actuator it came down to the N75. Funny thing was the N75 tested good statically. I have no means to test it dynamically and that was the problem, it must operate at around 20 hz or so. Putting in a new N75 fixed the surging. I did not replace any vacuum hoses or anything else since they all tested fine. I did break the ECU MAP sensor nipple though. :mad:
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI
The diaphragm on old N75s gets stiff and cannot function properly. Replace it. ~$50 for a Pierburg generic one.

Do the vacuum lines from the N75 while you have it all apart.
 

Sayray24

Well-known member
Joined
Apr 5, 2010
Location
Olney, IL
TDI
1998 VW Jetta
thanks for the info guys. what would be the possible consequences of just letting it go for now? seeing as how i usualy shift before or right around 3000rpm
 

Mike Piles

Veteran Member
Joined
Jun 11, 2000
Location
St Louis, MO USA
TDI
2000
The diaphragm on old N75s gets stiff and cannot function properly. Replace it. ~$50 for a Pierburg generic one.

Do the vacuum lines from the N75 while you have it all apart.

Could this be the very intermittant problem I have with my 2000? Once and a while it will fall on its face about 3000 rpm. You cannot get it to redline. It may do this 2 or 3 times, then everything will go back to normal and not do it again for 6 months.
 

Sayray24

Well-known member
Joined
Apr 5, 2010
Location
Olney, IL
TDI
1998 VW Jetta
well the jetta is going to the shop this week so hopefully they will find the problem
 

Sayray24

Well-known member
Joined
Apr 5, 2010
Location
Olney, IL
TDI
1998 VW Jetta
well the mechanic acknowledged that there was something not right but he could not pinpoint the problem. he thinks it might have something to do with the axel wearing out or something like that.
 
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