Subtle Stutter, Smoke, Low MAP, LIMP MODE.


Veteran Member
Sep 18, 2003
99.5 Jetta TDI GLS 165K. Clutch 5K ago after release bearing failure. N75 5K ago after diagnostic tests proved it to be the culprit responsible for "control boost deviation" limp mode garbage. Occassionally running Speedtuning box.
I've got long cranking time. Had it a few months ago, but a new battery did the trick - for a while, but it came back. Recently - within the last week or so, I've noticed, especially with the cruise on, that I get these surge "burps", followed by black smoke out the ass - of the car. I'll be cruising along and feel a subtle jerkiness, like the car dozed for a second and then called up some power to keep up with itself, then I can barely see the car behind me. Fun with tailgaters, but I'm driving cross country next week ( and towing a trailer with 2 motorcycles), so the novelty is wearing off.
Today I went through a puddle 2 feet deep, car stalled out, and I had to push it out. Fun. Waited a bit and started it back up. The glowplug light was blinking and the cel was on. Hooked up the Vag, and there'd been a short of some kind. It dried out, I cleared the codes, and it ran fine.
Until I got on the highway a few hours later and started up a hill under load. Limp mode. I re-booted and tried to make it happen again, but no dice.
Hooked the Vag up again and noticed that I've got low MAP under load. I request 1948 (or something) and it gives me 1500.
Now, me and NutsnBolts cleaned out my intake about 60K ago, and I've been running it with the modded EGR setting to bypass it, so I'm thinking a clogged intake mustn't be the problem. We checked all vaccuum hoses to figure out the N75 problem about 2 months ago, so I think I'm all set there. I was going to switch out the MAF for one I've got in the garage, but I've got good MAF numbers, and I don't imagine a bad MAF would affect Manifold Pressure in that way. I've GOT a new turbo sitting in the garage. I could just switch it out and see what happens.
But I'd like your brains on the first, Diesel Geniuses.
Have at it.


Top Post Dawg
May 21, 2004
Humboldt Co CA
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
Low MAP, but good MAF.

I don't know alot, but since one is available, I'd change the MAF and see. You have one, and it's easy.

The MAF doesn't usually cause a limp mode, but what the heck.

If that didn't do it, I'd then try to replace all vaccum hoses to the N75 that weren't previously changed. Small hole or minor split would cause a serious problem and cause limp mode. Also, the little tube in the ecu is interesting and can cause this problem. What did you do to deal with the lines before? Did you replace them? If not, do it. It is worth while since they could have gotten bad during the last two months. This is the general situation that causes limp mode.

Dump the speedtuning box until problem is resolved. Can confuse problems.


Veteran Member
Sep 18, 2003
Hey, sorry it took so long to get back. Turned out there was a big gash in the big hose that goes to the EGR. Replaced it - $57, ridiculous - and it was fine for a day. Now the problem is back. I'm guessing that once the system was properly pressurized, one of the other vaccuum lines gave out. I'm driving x-country next week, so I'm not taking any chances. I'm bringing it to the stealership to get checked out. We'll see how long it takes them to tell me I need a turbo. I'm guessing within 2 hours.