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

[JoeBags]

Thank you for putting a great guide together got me out of limp mode, slamming a full 90hp now

 

[JoeBags]

hello, I'm new to the forum, I have a tdi vw golf 1999 1.9 liter, manual transmission, love this car but recently got a scary sound from the engine, I heard a tap sound and smelled burning one morning. After that I got the following problems, engine starts slow, it takes a long crank time, 3 to 4 seconds in sacramento California area weather, after starting it, it runs smooth but has a knocking or rattle sound at the motor, this knocking sound increases as I put a load under the motor, the engine knocks at every speed, once in a while this knocking sound might go away for 2 seconds and come right back when i'm going down the highway, but it will only go away for this random 2 seconds at highway speeds, otherwise it's alway knocking or rattling. I saw some of the knocking sounds on youtube and their just a little louder than mine. Mine runs smooth, just the knocing noise and slow start up and slow acceleration. It used to be really quiet with lots of power, i got it smogged at a smog shop 2 weeks prior.

Every time i put it under a load, for example 1st gear, it will make this knocking rattle noise even more, especially if i put it in 1st gear partially let off the clutch with the break peddle pressed down, it aggitates the noise full blast (i did this just to diagnose where the noise is coming from). It sounds like an exhaust leak but the exhaust and motor mounts look good.

I checked the timing-it's dead on
I changed the fuel filter-no difference
I put in a new mass air flow sensor-still does it.
I opened the fuel lines just above the injectors while running the motor-plenty of diesel fuel comes out.
I took the cam cover off and ran the engine-it threw oil everywhere but i didn't see anything wrong in the cam shaft area.

While the engine is running in idle if i partially close the shutter valve where the engine shut off is (next to the egr) it will agitate the noise too. I can live with the slow start up and slow speed but the knocking sound is too serious to ignore. Sure would appreciate any help. Thank you

Sounds to me like a leak in your fuel line on the suction side. allowing a steady flow of air bubbles in. Does your rubber fuel line look wet? it doesn't necessarily leak fuel, like i said i think it's the suction side so fuel wouldn't come out it would let air in, however when the engine is shut down it would seep out of the line and make it look wet.

 

[@Tdi VW]

In time i did my log my actual boost was Nearly 3BAR and dint had a limp mode

 

[Uncle Karone]

I went to check out the silicon lines from McMaster-Carr and noticed in the description that theirs are "not rated for vacuum". Anyone had difficulty with these or how long you been using them with no problems? Just fixed the loose nipple leak at the vacuum pump by following this thread, thanks.

 

[davealltheway]

Hi All

Looking for some help. Just bought an old 2001 VW Jetta TDI. Guy didn’t tell me it has issues with limp mode of course.

I have read through all the threads and am hoping to fix it myself.

I can consistently put the car into limp mode by putting it in 5th, letting the revs drop below 2000RPM and flooring it. I can fell the turbo kick out in the pedal and its limp. Then I shut the car off and back on while driving, and turbo is back.

I thought I found the issue today, as there was no hose from the n17 (EGR solenoid) to the air cleaner. The hose was sitting there, but disconnected. Didn’t fix it .

I also cleaned the MAF (mass air flow sensor), but still no go.

Just looking for clarification on the MAF test. If I get the car in limp mode, and then remove the MAF harness, the power stays the same, limp, no turbo. But if the car is not in limp mode, and then I remove the MAF harness, it acts like I am in limp mode, slow and sluggish, plug back in and car runs well (provided I don’t tramp on it and put it back into limp)

Would you say my MAF is bad? Air filter is clean, snow screen cleaned. Visual check of all tubing. I don’t have a VAGCOM to check codes. Any suggestions would be appreciated!!

D.

 

[TNTKNC]

There are a lot of issues that can cause a limp mode. Depending on how the previous owner drove it, there is a good chance the vanes on the turbo are stuck with soot. Get under the car with a vacuum pump and see if you can active the turbo vanes at the actuator. If you don't have the tools then find the nearest guru to help you out. This is very likely a fairly simple fix and you will have the car you thought you bought.

 

[hgsmith]

The silicon lines from McMaster-Carr work great !! Easy to put on and should last longer than the oem.

 

[davealltheway]

Disable

I had an ex vw guy go through my system and he found now issues. He thinks its a computer glitch causing the error code 1556.

Anyone know how to trick the computer, I know it could cause issues should something else go, buts its an old car and I don't really care, just need it to last a year.

I read that grounding the MAP senator to the body would trick the computer. Any thoughts?
D.

 

[rdkern]

Did he check the vnt actuator for movement with vacuum? check the hoses to/from the N75? How clean is your intake? What did he use to pull the code? Generally, these things are not a computer "glitch".

 

[xjamesx]

0299 cel

Another 0299 CEL issue for this thread:
I normally like to fix what I can (with help from this site) or take it to Herm if I can't but I need to get this fixed ASAP before a quick road trip in 4 days. Any help is appreciated. Here is the breakdown:
'03 Jetta wagon - 213k miles - timing belt done 30k ago by Herm - Intake cleaned out 15k miles ago - a few small issues (coolant temp sensor) but nothing serious. Other than that - Perfect!! until the other day.
So I was driving on Sunday with the AC on in 80 degree weather with the wife. After I turned off the AC (used it for about 70miles), I was losing power in acceleration. I took it to get the code read and I had a 0299 CEL. After searching/reading this board for a long time, I think I am in a good direction.
I replaced the air filter and the hesitation was still there but not as abrupt. I unplugged the MAF sensor and it drove pretty much normal but just slightly under powered. No hesitation noticed. I cleaned the MAF with MAF cleaner and still have the exact same hesitation. I replaced one suspicious vacuum hose that turned out to be fine. All other vacuum lines seemed fine. When unplugging one of them, I still felt good vacuum in the hose off the N75.
I ordered a new MAF that I'll install tomorrow after it gets here and hopefully, it fixes the issues. I am worried though that it will still be here and I'll only have 3 days to fix it (between work schedule).
Any suggestions on this particular situation?
Thanks!!!

 

[slyk]

Hey all,

Looking for a little backup on my limp mode troubleshooting. My symptom is that under wide open throttle and heavy load (up hill), my car frequently goes into limp mode. I pulled the code today and it is shown here:

So far I have done the following:

Replaced N75 (before I had a VAGCOM)
Replaced all vacuum tubing
Checked N75 operation with VCDS (VNT Actuator moves, hard to tell how far but it looks like about 3/4")

No MIL and with the overboost I suspect the MAF has nothing to do with it.

Here's my plan going forward:

1. Disconnect MAF and take the car for a test drive. There is wn MIL and with the overboost I suspect the MAF has nothing to do with it.
2. I've heard that the N18 line can be plugged with a golf tee -- is this the line coming into the top of the N18 valve? If so, that's what I plan to do after checking the MAF
3. Purchase a MityVac and test the VNT actuator for leaks (I want one of these tools anyway)...
4. If found faulty, replace VNT actuator
5. If that STILL doesn't fix it, pull the turbo and clean/lube vanes (REALLY not looking forward to doing this...)

Am I on target here with my troubleshooting? Anything you would do differently? Thanks!

 

[uzi_cupra]

I have fixed this problem on many cars before however this time it has been a nightmare.
I changed a brake pipe from the master cylinder to abs pump.
The car was driven in and out of the workshop with the intake off and the pipe work from the intercooler however only to maneuvour the car. The car sat for a few days with the bits disconnected while I waited on the brake pipe.
Since fitting it the car has been going into limp with the CHARGE PRESSURE CONTROL: NEGATIVE DEVIATION code, if I restart the engine it will give me a little boost after 3500rpm.

I have gone through this entire thread and follows the troubleshooting advice but nothing seems to work.
I used vag com basic setting group 11 to see if the actuator is working, which it is. I do not have an n75 instead mine is the one with the vacuum control module which sits above one of the top mounts. I removed each vac line and connected a hose to each end, blew in and sucked on each to check for any leaks, but nothing.
I checked all intercooler/turbo pipework.
Checked brake booster pipe, brakes are fine too.
Rod length is fine, no sticky vanes,
Maf is mapped out,
Turbo wheel spins freely.

The car in question is seat Ibiza cupra tdi. Finished my build not too long ago and it was holding 2.2 bar no problem, was driving like a dream. If someone could help me out it would be great! Don't know what I'm missing.
Cheers guys.

One last thing, could the fuel filter be causing such an issue? It has not been changed for some time now..

 

[Ruffrida]

I have fixed this problem on many cars before however this time it has been a nightmare.
I changed a brake pipe from the master cylinder to abs pump.
The car was driven in and out of the workshop with the intake off and the pipe work from the intercooler however only to maneuvour the car. The car sat for a few days with the bits disconnected while I waited on the brake pipe.
Since fitting it the car has been going into limp with the CHARGE PRESSURE CONTROL: NEGATIVE DEVIATION code, if I restart the engine it will give me a little boost after 3500rpm.

I have gone through this entire thread and follows the troubleshooting advice but nothing seems to work.
I used vag com basic setting group 11 to see if the actuator is working, which it is. I do not have an n75 instead mine is the one with the vacuum control module which sits above one of the top mounts. I removed each vac line and connected a hose to each end, blew in and sucked on each to check for any leaks, but nothing.
I checked all intercooler/turbo pipework.
Checked brake booster pipe, brakes are fine too.
Rod length is fine, no sticky vanes,
Maf is mapped out,
Turbo wheel spins freely.

The car in question is seat Ibiza cupra tdi. Finished my build not too long ago and it was holding 2.2 bar no problem, was driving like a dream. If someone could help me out it would be great! Don't know what I'm missing.
Cheers guys.

One last thing, could the fuel filter be causing such an issue? It has not been changed for some time now..

Seems to be an ongoing problem for these TDI's i have having the same issues,

http://www.audi-sport.net/vb/a3-s3-...er-4th-5th-gear-around-1800rpm-limp-mode.html

 

[uzi_cupra]

Seems to be an ongoing problem for these TDI's i have having the same issues,
http://www.audi-sport.net/vb/a3-s3-...er-4th-5th-gear-around-1800rpm-limp-mode.html

have you checked your actuator rod length? you sure you have checked for split hoses?

 

[Ruffrida]

have you checked your actuator rod length? you sure you have checked for split hoses?

Yeh adjusted it took it for a run then re set it again.

I am now thinking it is the lower inter-cooler pipe from the turbo.
So i have heard these tend sagg and rub on the drive shaft and split them very very slightly

Cheers

 

[uzi_cupra]

I have fixed this problem on many cars before however this time it has been a nightmare.
I changed a brake pipe from the master cylinder to abs pump.
The car was driven in and out of the workshop with the intake off and the pipe work from the intercooler however only to maneuvour the car. The car sat for a few days with the bits disconnected while I waited on the brake pipe.
Since fitting it the car has been going into limp with the CHARGE PRESSURE CONTROL: NEGATIVE DEVIATION code, if I restart the engine it will give me a little boost after 3500rpm.

I have gone through this entire thread and follows the troubleshooting advice but nothing seems to work.
I used vag com basic setting group 11 to see if the actuator is working, which it is. I do not have an n75 instead mine is the one with the vacuum control module which sits above one of the top mounts. I removed each vac line and connected a hose to each end, blew in and sucked on each to check for any leaks, but nothing.
I checked all intercooler/turbo pipework.
Checked brake booster pipe, brakes are fine too.
Rod length is fine, no sticky vanes,
Maf is mapped out,
Turbo wheel spins freely.

The car in question is seat Ibiza cupra tdi. Finished my build not too long ago and it was holding 2.2 bar no problem, was driving like a dream. If someone could help me out it would be great! Don't know what I'm missing.
Cheers guys.

One last thing, could the fuel filter be causing such an issue? It has not been changed for some time now..

Anyone have any ideas what could be going wrong?

 

[Ruffrida]

Anyone have any ideas what could be going wrong?

Have you do any live data through vag-com or run a fault code whilst in limp mode?

I should hopefully have mine today so will let you know what that said.

 

[uzi_cupra]

Have you do any live data through vag-com or run a fault code whilst in limp mode?
I should hopefully have mine today so will let you know what that said.

I am getting charge pressure control negative deviation.
No point doing any logging as its in limp so wont get any real WOT readings, MAP is fine (4bar sensor) and my MAF is mapped out.
Annoying thing is the car was running absolutley fine for 2000 miles after my build and i replaced a brake pipe-ever since i've had the problem.
I have stripped and fitted and restripped and pressure tested all hoses-no leaks!

 

[Ruffrida]

Thats a bit random !!

Has the vac pump been vac tested ?

Was the pipe brand new ?

It still sounds like a split pipe to me, i am on a hunting mission at the moment as i have the same issue just cant put me finger on it, really annoying. I am now heading more towards the turbo pipes as these get very brittle and mine was stood for 3 months before this happened.

You have got to remember with these diesels it only takes a minor leak and it troughs proper fits, audi, seat, vw & skoda are all known for it.

I have even added to sealant to all vac pipes to ensure there is no leak there.

Dont worry fella ya not the only one, i have been going round in circles for months

 

[rdkern]

If it was caused by the brake work, you might be able to retrace your route to see what you could have mistakenly disconnected? Or boost tubes that you may not have completely connected? How do the brakes work now? Good response (ie, good vacuum?)

 

[uzi_cupra]

If it was caused by the brake work, you might be able to retrace your route to see what you could have mistakenly disconnected? Or boost tubes that you may not have completely connected? How do the brakes work now? Good response (ie, good vacuum?)

This is why I'm so confused, I haven't only retraced my steps once but on several occasions and everything is in tact. I am just about to change my fuel filter, and then re check all vacuum lines AGAIN with my vac pump..
Here's to hoping!
Brakes feel great!

 

[uzi_cupra]

Changed air filter, fuel filter and cleaned the connection points on my vacuum control module but still same problem. Before I change anything I will get it in the air once again and have another look at it with a friend. Hopefully a second set of eyes will help!

 

[BobnOH]

yea, isolate the leak with some soapy water or something. Check especially at the fat pipe going to the brake booster, or it could up around the N109

 

[gcodori]

I had a broken plastic T between the vaccum line and the brake booster. Was hard to find due to being close to the firewall.

Sent from my super awesome phone thingy.

 

[uzi_cupra]

Ok spent the whole weekend trying to fix the car...
I pulled all my pipes off my Vacuum control module and pressure tested each one. Actuator holds more than enough vacuum, vacuum reservoir holds plenty vacuum too. the brake booster pipe was removed, stuck my thumb on one end and vacuum tested to ensure it was not leaking and this was absolutely fine too.
After putting everything back together it is still the same.
I do get boost but only after 3000 rpm, and I only get max 1.5 bar instead of 2.2.
When it does boost it chokes for a split second and boosts and chokes and boosts again. As though there is a shortage of fuel. I changed the fuel filter just last week.

Still coming up with negative deviation - im starting to think it could be my actual vacuum control module??

 

[rdkern]

When you were playing with the vacuum, did you make sure the actuator moves freely?

If so, I'd be leaning towards the N75 valve - the thingy that puts the vacuum to the actuator when the ecu wants it to. I think you can test it with VCDS, although I've never done it.

 

[Ruffrida]

Ok spent the whole weekend trying to fix the car...
I pulled all my pipes off my Vacuum control module and pressure tested each one. Actuator holds more than enough vacuum, vacuum reservoir holds plenty vacuum too. the brake booster pipe was removed, stuck my thumb on one end and vacuum tested to ensure it was not leaking and this was absolutely fine too.
After putting everything back together it is still the same.
I do get boost but only after 3000 rpm, and I only get max 1.5 bar instead of 2.2.
When it does boost it chokes for a split second and boosts and chokes and boosts again. As though there is a shortage of fuel. I changed the fuel filter just last week.

Still coming up with negative deviation - im starting to think it could be my actual vacuum control module??

I would get a vac tester on your pump, it sounds like you have fixed the leak now the pump cant keep up.

Adjusted the actuator on mine at the weekend, so close to been a flying machine, just needs maybe one more turn at least

 

[R-2]

Candian Grizzly This is R-2 I see your from BC Could it be your close to Grand forks or Christina lake?

 

[flydope71]

Be sure to check all the nipples for your vac lines! Especially if you had a previous vacuum leak. I had two nipples plug on me and some times boost was intermittant. The small nipple on the booster check valve plugged up on me when my actuator had a leak. I also had the small check valve plug up on me a different time. Easy to check and cost is Zero$$

 

[TheLongshot]

Gods, I hate this issue. I've been suffering from this for a couple years now and I just can't find a solution. Replaced MAF, replaced N75, replaced vacuum lines, tested turbo actuator and that's fine. I still have the damn problem.