limp mode again!

Hi all,

So at random times of starting my car it will go into limp mode. I have done a ton of research on limp mode, and Ive been fighting it for a couple months now trying to trace it. so far it's not going well. I have changed the maf with a new one... no difference... put old one back in. New vac lines... no change. actuator moves full motion. I put in a n75 valve today and the first couple starts and short test drives nothing, 3rd start and its running fine. Problem is that it always does this, so i don't know if this is for another week until it loses boost again or what because it's always at random. Any ideas?? cause im clueless this is sooo weird!
Thanks for your time,
Glowbugtdi.

This car does have an egr delete if that makes a difference...

You said the VNT arm moves full throw, are you sure?
Does it hit the max stop?
At what vacuum does it start to move?
At what vacuum reading does it take to get to the max stop? Normal range is at 3” it starts to move , and around 18 “it should be at the max stop.

Does the actuator actually move smoothly, or is it rachety?
The same with the lever when disconnected, does it move freely like flopping from on end to the max stop?

Most of my limp issues have always been in these areas, I have 5 TDI’s to compare things.
Just my .02

So you have done VCDS boost graphs?

it moves full throw if i move it. I don't have a mighty vac (apparently i should get one sooner than later) so I don't know when it moves. the odd thing tho is that it will work just fine for days then just suddenly go into limp, so for right now its ok.... but i don't know for how long. The actuator moves smoothly but feels spring loaded, it's stiff enough that it kinda hurts the fingers when I pull down on it. i haven't disconnected the actuator because far as i could tell it was ok, and i didn't know how to re set it (ive heard that you have to re set it to a certain position as not to over/under boost).

unfortunately i don't have vcds. It was on my list but it never happened, and honestly I wouldn't know how to run it even if i had it. I don't know how the codes work, my knowledge on vcds is pretty minimal.

thanks for the help!

I have read that it could be the ecu, but i don't know how that figures...
then again i don't know where the ecu is, or how i would check if thats the cause.

Have you checked the brake booster vacuum hose? That can develop a hidden crack.
Get yourself a MityVac (Harbor Freight ones are OK) and test the turbo actuator too.

flee said:

Have you checked the brake booster vacuum hose? That can develop a hidden crack.
Get yourself a MityVac (Harbor Freight ones are OK) and test the turbo actuator too.

Click to expand...

im not entirely sure what a brake booster is, but ill look into it.
thanks

GlowBugTDI said:

im not entirely sure what a brake booster is, but ill look into it.
thanks

Click to expand...

Maybe in your case get a MityVac and test the vacuum system methodically.
Take pictures of the hose connections before you start to be sure they get
reconnected in the right way. See what vacuum the pump is producing and check the
nipple at the pump. These are known to work loose over time and leak.

hey so i got a silverline mity vac... yay!. now on the gauge it says lbs. of mercury my question is at how many lbs. will it move? is it still the 3-18? idk if this is the same kind of gauge that all of them have or not....
Thanks

Vacuum is measured in inches of mercury. This refers to the height of a column of
mercury above the surface of the reservoir of an old-fashioned liquid vacuum gauge.
None of that matters but 'pounds' of mercury doesn't figure into it.
If it has 'pounds' on the dial it probably is referring to 'psi' of positive pressure.
Start checking the vacuum of your system and report back.

flee said:

Vacuum is measured in inches of mercury. This refers to the height of a column of
mercury above the surface of the reservoir of an old-fashioned liquid vacuum gauge.
None of that matters but 'pounds' of mercury doesn't figure into it.
If it has 'pounds' on the dial it probably is referring to 'psi' of positive pressure.
Start checking the vacuum of your system and report back.

Click to expand...

oops sorry yes it's inches... someone else used the (") sign, and i confused myself lol sorry.

ok new actuator and still limp! uggh so maddening... sooo what else can i check? one thing i noticed is that the turbo waste gate arm thing that the actuator bolt/arm pivots on moves very freely. like i can flick it up and down super easily is this normal? another thing is that my brakes act up every now and then they get real stiff when the car starts.... idk. any advice would be greatly appreciated as this is clearly above me. I have recently tried getting in touch with a tdi mechanic in my area, but haven't heard back from him. next thing i wanna check is brake booster or the actual pump, but i need to figure out how i check that still. back to doing more research oh joy!
thanks all!
GlowBug

Did you try to get in touch with Paramedick? He's in Cambridge and is very knowledgeable in regards to DTI's. Sounds like a vacuum problem since the brakes are stiff.

GlowBugTDI said:

ok new actuator and still limp! uggh so maddening... sooo what else can i check? one thing i noticed is that the turbo waste gate arm thing that the actuator bolt/arm pivots on moves very freely. like i can flick it up and down super easily is this normal? another thing is that my brakes act up every now and then they get real stiff when the car starts.... idk. any advice would be greatly appreciated as this is clearly above me. I have recently tried getting in touch with a tdi mechanic in my area, but haven't heard back from him. next thing i wanna check is brake booster or the actual pump, but i need to figure out how i check that still. back to doing more research oh joy!
thanks all!
GlowBug

Click to expand...

I take it you test the actuator with the miteyvac and found it was not operating properly, ie not holding vacuum and not moving correctly through its travel? Stuck turbo vanes can keep the actuator from moving them, so if you changed it out, the problem can still be there.

yep tested with mighty vac, and the old actuator didn't move at all. it wouldn't hold vacuum. the vanes must be moving tho because the turbo vane arm moves.... though it is very floppy so idk if that makes a difference.

i'm afraid i haven't heard of paramedick... i had tried getting ahold of nick (greengeaker). Do you know how i can get ahold of paramedic?

So i fixed a crack in the brake booster cable, and still no boost. Unlike the floppy turbo waste gate arm yesterday it is stuck today. like i can't even pull it down like forcefully with my hand its as if it's seized, but then if i pull on it a couple more times it will move. What the heck is going on?? tomorrow im gonna call a diesel mechanic in a near by town and see if i can send it in. i am so confused...

ok, so im working on the car and if my turbo waste gate arm is moving really freely almost as if its not moving anything inside would that mean my waste gate is broke? i mean when i move the lever it doesn't sound as if it's moving the whole vnt system or anything... so broken maybe?

I would expect there to be at least a bit of resistance at the lever - it's moving many
not very pristine vanes and the control ring. So yes, there may be something amiss...
Not really a waste gate but a VNT system but everyone here knows what you mean.
And as for taking your TDI to a diesel mechanic, any well regarded auto repair shop is
OK for a turbo replacement - the job is the same mechanically as a gas engine turbo,
even the VNT-15 is the same part IIRC. Just don't let them talk you into a timing belt!

ok, thank you so much!! didn't know the difference between waste gate and vnt but that makes sense thanks for that. i have learned so much through this forum, it is literally the best forum i have ever been on! sooo i went and decided to go through everything again, and found that apparently while i was fixing the brake boost hose the actuator i just put in had loosened the nut and the arm moved causing the actuator to not open up much. re tightened that nut (a bit tighter this time) and put some glue on it and the GlowBug lives again! and it's about time because my friends/family are starting to doubt the tdi life and fame. a huge shout out to everyone who helped me find this problem, and directed me on what to check! You guys saved me lots of money, and time that would have been spent trying to figure it out on my own.

thanks again,
GlowBugTDI

Good to hear!

Had limp mode due to bad EGR after turbo failure on 9N 1.9TDI. After many weird anomolies, turned out the bleed vac back to the air box was blocked. Symptons, no power low, hesitation and then BOOST....

Up to that point the EGR was leaking and I'd also check all your pressure hoses. often split. Ours once in Limp Mode restricts fuel and wont get on boost