No Power Over 3,000 RPM

Yaco

Member
Joined
Oct 26, 2006
Location
NYC
TDI
1998 VW
This is a problem with my 1997 TDI that went away for several years and has returned, but it is worse. When I am going up a hill and pushing the car past 75, the car suddenly loses power and the engine runs roughly. The car then has decreased power going up hills and will not go over 3,000 rpm. If I shut the car off and turn it on, it is back to normal, as long as I stay at lower speeds.

Previously I was able to turn the engine on and off and the problem would correct itself for a longer period of time. Now the problem will not go away.

I was at very high elevations in Mexico for several months, and the problem cropped up when I returned to lower elevations. That probably has nothing to do with anything, but I thought I would mention it.

The check engine light has gone on, but I am away from home and my mechanic and wanted to get a sense of the problem to see if I should get it addressed before my long drive home.


Thanks
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
Your TDI is going into limp mode due to a problem in the turbo boost control system. The ECU sees too much boost pressure, is unable to control the boost pressure, so it cuts fueling to protect the turbo and engine.

The most common causes are leaking boost control hoses or a failed N75 boost control valve. The N75 valve is mounted on the passenger side fender just ahead of the fuel filter, and has 3 control hoses - red, blue and black - connected to it. The red and blue hoses go to the turbo, and if one of them is damaged or disconnected that will cause your problem. Also check the electrical connection to the N75 valve.

You won't hurt the car by driving it home in limp mode, but it won't be much fun :(

Simon
 

Ironforger

Veteran Member
Joined
Feb 18, 2003
Location
Lawrenceville, NJ.
Check the car with Vag-com. You might see a "charge control deviation" erorr of some sort if the N75 is bad.

There is always the possibliity of the maf going bad too.

Don't forget to verify if the check valve is working. (take note of the exact direction before removing to test, it's a directional component.) You should be able to blow though one end, but not the other. Can be cleaned with a light solvent and a light blast of compressed air.
 

whitedog

Veteran Member
Joined
Jul 12, 2004
Location
Bend, Oregon
TDI
2004 Jetta that I fill by myself
I am guessing that Yaco is in Mexico right now. That would mean that Vacuum hose may be readily available, but an N75 may not be so easily available.

Isn't the Valve for the EGR the same valve? If so couldn't that be swapped over to get the car across the border and to someone like Runonbeer to help get things right?
 

alphaseinor

TDI Innovator, Gone but Not Forgotten
Joined
Jul 30, 2006
Location
Denton, TX
TDI
'03 Jetta TDI 780,000 miles (totaled out), 01 Audi TT 225 Quattro 230,000 Miles (runs great!), 00 Cabreetle Beetle dash, ALH & MK4 harness Swap
Trust WhiteDog, He knows his foreign parts (long story on his end)... The N75 may be hard to find in me-hee-co. Vaccum hose... never had to ask...
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
whitedog said:
Isn't the Valve for the EGR the same valve?
On A4 cars, boost and EGR are both vacuum controlled and the valves are the same.

On A3/B4 cars (like Yaco's), EGR is vacuum controlled but the wastegate turbo is controlled by boost pressure and the two valves are not interchangeable.

Simon
 

whitedog

Veteran Member
Joined
Jul 12, 2004
Location
Bend, Oregon
TDI
2004 Jetta that I fill by myself
P2B said:
On A4 cars, boost and EGR are both vacuum controlled and the valves are the same.

On A3/B4 cars (like Yaco's), EGR is vacuum controlled but the wastegate turbo is controlled by boost pressure and the two valves are not interchangeable.

Simon
Thank you. I knew about the vacuum/pressure part but wasn't sure if they were still interchangable.
 

wny_pat

Top Post Dawg
Joined
Apr 7, 2004
Location
Western New York State
TDI
2002 Jetta TDI
The vacuum hoses get tiny pin holes in them. You can't even tell their bad. Just replace them including the short one in the ECU. It's right on time.
 
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