Diagnosing and Fixing Limp mode for A4 1.9TDI [low power troubleshooting]

[rdkern]

What reading do you get on the vacgauge? Do you have the necessary vacuum? Based on the "thumb pressure" it takes to move this puppy, I'd guess you're pump isn't drawing sufficient vacuum.

Boost being "laggy" is more likely to be an intake issue - clogged air filter (when last changed? If over 40K (or close to it, or serious dusty conditions) change it. Snow screen? ect.

 

[Turbosprezarka]

But the pump will not show it pulling any vacuum. The pump will pull vacuum on other items. It should only take 3-5"Hg of vacuum to actuate the VNT rod, the hand pump's gauge goes to 30"Hg.

 

[bmwvw]

But the pump will not show it pulling any vacuum. The pump will pull vacuum on other items. It should only take 3-5"Hg of vacuum to actuate the VNT rod, the hand pump's gauge goes to 30"Hg.

Sounds like your accuator has a small hole in it like mine did. Just replace it and you will be fine.

 

[Turbosprezarka]

Sounds like your accuator has a small hole in it like mine did. Just replace it and you will be fine.

Is this possible though? Vag-com group 11 will cycle the N75 (which you can hear), and you can see the rod move. But when I put a handpump to it, nothing happens.

 

[rdkern]

It sounds to me like you're doing something wrong with the handpump. I can't imagine what - but you should be hearing a leak if there is one, and getting some evidence of vacuum if you're pumping on a semi-closed system. If the hole was big enough to keep you from causing a negative pressure with your handpump, I'd suspect it wouldn't cycle really nicely with the N75/other system.

 

[bmwvw]

Well if you verifyied the pump, hose and the N-75 valve this would be the last place to look for a vacuum leak. The vnt accuator should hold vacuum.

 

[Turbosprezarka]

It must be that the VNT has a pin hole, where the steady vacuum of the engine can maintain a reduced fraction of its operation...and the hand pump just won't show it holding any vacuum because it isn't constant.

 

[zoot]

I asked a answered question. Deleting it.

 

[jeffro1979]

I just read this and wow, sure sounds like what I'm seeing. Mine seems to happen more in hot weather. Does anyone have any input on that?

 

[Canadian_Grizzly]

I just read this and wow, sure sounds like what I'm seeing. Mine seems to happen more in hot weather. Does anyone have any input on that?

Check the routing of your vacuum lines. If hot weather has an effect it could be a line too close to the manifold and collapsing when the rubber is hot and pliable.

 

[jeffro1979]

thanks

thanks for the input, I'm going to work on it this weekend and we'll see how it goes. thanks all

 

[marcus_ishere]

On that note...

Okay, I have the same issue. But I have replaced the n-75. I have cleaned the intake and turbo 20,000 miles ago.. I just straight piped my baby, and the cat wasnt the issue. I get it too. But what I believe is that I have a faulty egr valve controller. My solution is the racepipe by dieselgeek and egr delete. Who knows? if I do put this part on.. What is it going to do to my Ecu? And how do I cut the controller out of my Ecu? Vag Com?

 

[Briank2]

N75 Valve

After reading the forum on "limp mode" my N75 valve clicks constantly right after I turn the ignition switch on, and I get an intermittent limp mode situation. I had a diognostic done and was told my ECU had an internal error. Could this cause the limp mode problem. I changed out the N75 valve and it does the same thing. Any input greatly appreciated.

 

[SheeB]

Canadian Grizzly,

I may be wrong here but according to your link for the McMaster replacement tubing, for the Viton tubing you have 5119K41 @ $3.69/ft. listed as "firm" where as on the McMaster catalog its listed as 5119K79 @ $3.22/ft.

 

[Canadian_Grizzly]

The part number has probably changed...go with the description.

 

[Pizzadub]

I've had two limp mode situations in the last 5,000 miles, which is all that I have owned this TDI. 1999 NB 207,000 miles. Once engine cold pushing it up a steep hill and the other pushing it on an on ramp. Cycling the ignition cured it. Never had a CEL yet. Outside temp 25 'F both times. I've read this whole thread and I'm going to check for vacumn leaks. With no codes am I just not pushing the car enough normally because I shift at 2,000 or less RPM's or am I working into a common problem?

 

[rdkern]

If you're shifting at 2000 or less, you're not exercising the VNT controls enough, and they get clogged and don't respond as the ecu wants them to. Use the power more often. Don't shift until 2500-3000, and use more of the "go" pedal. You won't take much of an economy hit, and it's good for the car.

 

[rosher]

Are you shifting at 2000 b/c going higher causes limp mode to occur?

 

[Pizzadub]

I don't push the car because I think I'm getting better economy. I'll drive 100 city miles at work for delivery and never get past 45 MPH or 2,000 RPM. The incident at the on ramp was at the end of the night and going home aftrer a 100 mile city journey. This has only happened twice and the car produces normal power all the way to the redline other than these two instances.

 

[Canadian_Grizzly]

"Pizza"dub you got to give it a good ol Italian workout once in a while. Also check you intake for coke...ie cloggage. Remove pipe coming out of EGR and take a look.

 

[rosher]

Yah, shifting 2500-3000 sure isn't 'pushing' the car. Lugging the engine will get the vanes in your turbo stuck (as mine were when I bought my Golf). Depending on where they stick, your car will go into limp mode when the turbo winds up too fast. Doesn't sound like your vanes are stuck but they could be sticky... Like griz says, spool it up a little bit. I bet you won't see the decrease in mileage you think.

 

[bmccrea]

Here's my situation.

03 Golf TDI

Twice in the last week its gone into what feels like limp mode. I take off from a stop light, shift to second. When it hits 3000rpm it just stops accelerating at the pace it was before, and just slowly slowly increases speed. If i back off, and hit the go pedal again, it pretty much just keeps the rpm constant, doesn't really accelerate or anything. No CEL both times. Cycle the ignition and everything is good to go.

Both times the car wasnt at 90c, about 1/2 way up the dial.

Is this limp mode even though i'm not getting a code?

 

[rdkern]

Sounds like limp mode. Are you sure you're not getting a code? No CEL apparently, but sometimes the code is set and the CEL doesn't come on.

 

[ymz]

Is this limp mode even though i'm not getting a code?

If it gets fixed by turning the engine off and back on, it was limp mode...

If it's safe to do so, you can stay in gear and while driving, turn the ignition switch off, wait a second, and turn it back on... [edit: won't work if you have an automatic transmission...]

Most likely the vanes in your turbo are stuck...

Yuri.

 

[bmccrea]

I'll scan it tonight and see if there's anything.
Would it show up in the engine controller?

It seems random right now. If the vanes are sticking, they must be coming unstuck as when i cycle the ignition everything is normal. Is there anything i can do to alleviate the problem... perhaps to avoid having to remove the turbo and clean the vanes?

 

[ymz]

If the vanes are sticking, they must be coming unstuck as when i cycle the ignition

Nope... it's that the ECU turns off the boost to protect the turbo... once you cycle the ignition, the ECU gives it to you again...

You can get under the car and "excercise" the actuator manually to help unstick it... you can give it an italian tuneup every time you go onto a highway... sometimes it's too badly carboned and needs to come off and be thoroughly cleaned... sometimes, it's actually broken...

Yuri.

 

[bmccrea]

You can get under the car and "excercise" the actuator manually to help unstick it...
Yuri.

Good info. thanks.

I was just reading about someone exercising the actuator manually and figured i'll head under this weekend and take a look at what's going on there.

It also seems like i should be cleaning my intake manifold. These problems seem to be related (from searching and surfing the forums) The car has 104k kms on it. I popped off the intake hose going to the EGR and had a look inside... it didn't look bad, but again, its hard to tell without taking it off and looking at the other side.

 

[alphaseinor]

It also seems like i should be cleaning my intake manifold. These problems seem to be related (from searching and surfing the forums)

you know... the first two posts in this thread have the most information on the subject... it's not a just throw ideas at it...

it's down to a psudo science... kinda like George Norie... but more accurate...

 

[bmccrea]

it's not a just throw ideas at it...

Is it not related? its mentioned in the first post...

 

[Raimieb]

brand new turbo, limp mode

BRAND NEW TURBO ABOUT 1 MONTH AGO, experiencing limp mode, going to install all new silicon vacuum lines and a new egr solenoid (had it for a while, just haven't installed, also, replacing my stock ccv with a dynaflow...i will do each one separately as to help narrow down the problem and let you guys know how it goes, just cleaned intake about 10k ago, so that should be fine...rock on!
is it possible that the new turbo is boosting too high and causing problems? car is not chipped yet, but i would like to square this away as april 26th GTG in Asheville is right around the corner...
anyone with similar turbo experience...must be vacuum line or n75 valve.