Hi folks forgive me if this has been asked before, but search is not my friend right now. Anyway, I'm currently 500 miles from home on a business trip, car (2002 Jetta TDI 5 Speed) was running great. Filled up, took off, and noticed no or little turbo boost. Normally my gauge runs between 15 and 20 psi under load, but now, I get no more than 5 psi on my gauge. If I'm going up a mountain grade, I have to floor it in 4th gear to maintain a steady 5 psi and usually get only 60 mph at best. On flat stretches it will run 80 or better no problem, just moderate acceleration and never more than 5 psi of boost. There is no CEL, or black smoke even floored going up hill, no weird smells or sounds, is getting 50 mpg too. I am getting SOME boost as I can see the gauge moving between 0 and 5 psi, but definitely not full boost. Any ideas? N75 maybe? I will look it over as I can in the AM, but I am limited on troubleshooting until I get it back home. Thanks for any help.
Sudden low/no turbo boost
- Thread starter psaboic
- Start date
STDOUBT
Veteran Member
That's a tough one.
Very weird there is no CEL. Are you sure there are no weird sounds?
Might be hard to tell from inside the cabin. I would run in and pop the hood for a listen.
Inspected all the vacuum tubing? How is your oil level?
Not classic limp, where it "resets" after power cycling?
Very weird there is no CEL. Are you sure there are no weird sounds?
Might be hard to tell from inside the cabin. I would run in and pop the hood for a listen.
Inspected all the vacuum tubing? How is your oil level?
Not classic limp, where it "resets" after power cycling?
Not sure if it is reset or not. I ended up driving another 300 miles to my hotel before I shut it off for the night. I will check for vacuum hose issues, sticking actuator, etc in the daylight. Just wondering if anyone had any ideas off the top of their head. Oh yes, oil level is fine, right between the marks on the dipstick.
Ok, checked everything I could.....hoses, turbo actuator, etc.. All checked good. Fired it up and it worked perfectly, normal boost every time I needed it. So.....it looks like it was classic limp mode. If it comes back again, I'll get a new N75 valve.
Powder Hound
Top Post Dawg
- Joined
- Oct 25, 1999
- Location
- Under a Bridge, Crestview, FL, USA
- TDI
- '00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
Yes, because limp mode is caused by a bad N75 EVERY FREAKIN' TIME!! 
Sarcasm aside, limp mode can have a number of causes, so some trouble shooting is in order before you start throwing parts at the problem.
Good luck!
PH
Sarcasm aside, limp mode can have a number of causes, so some trouble shooting is in order before you start throwing parts at the problem.
Good luck!
PH
oilhammer
Certified Volkswagen Nut & Vendor
OBD works, start there.
If it was a loss of boost, or too much boost, as the cause of limp mode, it will have flagged a DTC, although it may need to do it on more than one drive cycle to do so.
And your diagnostics will be different for either of those boost control related faults.
If it was a loss of boost, or too much boost, as the cause of limp mode, it will have flagged a DTC, although it may need to do it on more than one drive cycle to do so.
And your diagnostics will be different for either of those boost control related faults.