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

[taugust]

So, you are boosting 16PSI while going up that hill, WOT, and can't accelerate? ?
Please clarify...........

Yes, that was the case. Tonight, I believe I solved the puzzle.

One piece of the puzzle I forgot to give last night, since the intake cleaning was a week and a half ago: I did not get an EGR to Intake Manifold o-ring gasket before I pulled everything apart. The o-ring was flat and hard, but I put it back together because I didn't have a replacement. Next day, the dealership had to order it, so I just got it today and put it in. Viola. Good seal between the EGR and Manifold.

I have not tested on the big hill, but it doesn't have the sluggishness that it had. It was basically leaking charged air. The boost guage tap is in the hard pipe between the intercooler and the rubber elbow hose to the EGR, so it was seeing good boost, but it wasn't getting to the intake manifold at high boost.

Again, thanks to all the knowledgeable folks who pointed me to the possible causes and allowed me to work it out without the dealership. Mine was a combination of several of the possible causes, with some others thrown in. Lesson: Replace all the gaskets when you take everything apart.

Regards,

Tim

 

[taugust]

After driving to work and back, it is still not completely fixed. It is a marked improvement, but the car still lags somewhat on the long steep climbs. I will look into opening up the exhaust and looking at the cat converter.

 

[greendubs]

Limp Mode Help...

Hi all, I'm posting this question as I've researched as much as possible the cause of limp mode on my GTTDI PD115 Golf and so far no joy!!

I've run the Innotec turbo cleaner kit through the system twice, the actuator rod move smoothly and 1" or so. I haven't checked the vaccum test on the actuator yet but don't think it's at fault.

Two things I have noticed that my help diagnose are....

A: There is a distinctive wooshing sound when I blip the throttle to around 1400rpm... suggesting a vac leak but where..?

B: I notice this post mentions the MAF should be the first palce to look and when disconnected if it no longer drops into limp mode the MAF is at fault... I've disconnected mine to find it went straight into Limp mode.... is that significant?

Can anyone shed some light on the subject?

Thanks all

Matt

 

[Thorne]

An update as promised -- still no joy with my overboost / limp mode issue. At this stage the only thing to do is clean the turbo itself, but I'm going to wait on that for awhile. Tempting to try the oven-cleaner method but not really up to doing it myself...

 

[Yreka]

Has anyone just given up and installed a manual valve like this ?

http://www.3barracing.com/product_8.htm

I understand that its a band aid fix for something not working right, but Im about at my wits end with my own issues and running out of areas to fix
.
http://forums.tdiclub.com/showthread.php?t=281199

 

[Tom W.]

using a boost control valve

Has anyone just given up and installed a manual valve like this ?

http://www.3barracing.com/product_8.htm

I understand that its a band aid fix for something not working right, but Im about at my wits end with my own issues and running out of areas to fix
.
http://forums.tdiclub.com/showthread.php?t=281199

Yes, I've used one. Takes a while to dial in, but it does control overboost, including overboost spikes.

 

[pepper10]

Has anyone just given up and installed a manual valve like this ?

http://www.3barracing.com/product_8.htm

I understand that its a band aid fix for something not working right, but Im about at my wits end with my own issues and running out of areas to fix
.
http://forums.tdiclub.com/showthread.php?t=281199

Yup. Have one. It failed and cause my N75 and vane actuator to fail. See my post.. Still wouldn't go without one. Just clean out the hose from the intake to the boostvalve and the valve itself at every timing belt change and you will be fine.

 

[pbdr]

Great long thread. After almost 1.5 years of driving with this issue, I decided to go back to the basics and follow step one. New air filter and changed all the vacuum hoses, the car's back baby!! Did the vanes cleaning with no change.

So, before you invest the time doing the more difficult work, change/check the easier things.

Thanks for all the material here.

PBDR

 

[inspector404]

I have limp mode and the engin service light goes on and the fault codes are P0101 MAF senser and P3131 o2 senser low voltage. The P3131 is classified with the gasoline engin in my shop book. Help, what should I change or check?

 

[soylentgreen]

I have a very situational limp mode isue (po234): It happens on 2 occasions almost the exact same place.
1. Hill climbing at high altitude (about 8,000ft); about 60-70% throttle, 15psi of boost.
2. After engine breaking (coasting down hill in gear)
I believe my tune is good for 18psi. My boost valve stops a spike at 21 and regulates sustained boost at 19psi. I cant get it to hit limp mode at full throttle.
Last summer I replaced all vaccume line and n75 valve and replaced the MAF. My acutator will blead 1" vaccume over 5 or 10minutes.
Any ideas?

Interesting: tonight I had a very similar experience : 2002 NB TDI Automatic. Was driving up and very down steep hills, using engine breaking in 1st on the way down. Altitude was about 1500 feet above sea level.

After I hit the bottom of the hill and got back on the freeway, discovered weak power (I could do about 70mph tops with WOT) and got the P0234 code when I returned home.

The fact that we both had P0234s after engine braking is suspicious. Does engine braking on a TDI generate really strong vacuum like it does with a gas engine with a throttle plate?

 

[riofrio]

I'm in the process of replacing all the vacuum lines in my 2002 A4 and was wondering what is the best way to access all the lines by the N18. There is a couple of wyes back there too, and they are being blocked by two coolant lines (pic below). Any suggestions?

 

[windigo]

Does engine braking on a TDI generate really strong vacuum like it does with a gas engine with a throttle plate?[/QUOTE]

I was told that diesels have no vacuum. My boost gage never goes into
the vacuum area... even when going downhill with zero throttle....
To get vacuum our diesels have a vacuum pump that should put out
about 26 in.hg vacuum... hope that helps.. jeff

 

[windigo]

solentgreen;
There is no vaccum in a diesel engine. to get vaccum we have a pump which should
make about 26in hg. When I run downhill with throttle off my boost gage never
goes into the vaccum area... hope this helps... I tried to increase my mileage by
using engine braking at every chance. That did not increase my mpg and
I used 1/2 quart of engine oil in 1000miles in my 99 bug with over 200kmiles.
I now coast ever chance i get and I add 1/2 qt in 10,000miles...
happy trails
jeff

 

[FXDL]

The check valve # 7 [beginning of limp mode post]go bad in time so remove and replace with new vaccum hose only. The valve is not needed, but if you feel better running one then just install a new check valve as they plug up for some strange reason causing big problems or become part blocked. With the old check valve off blow through it and you will see how restrictive the old one is and maybe plugged. A new one is very restrictive even. On my old 2001 that I gave to one of my kids, the check which was part blocked has been removed all together and replaced with new vaccum hose only. The check valve just may be the problem for most out here even if they are partly plugged. It may have been talked about, but to read all on this posting would take for ever so my 2 cents or 1

 

[bradbates]

"2. connect a vacuum hose directly from the rigid brake booster vacuum line to the 'vac' port on the N75. You'll get an EGR code, but your turbo oughta work great."

What if this fixes the CEL that I was getting, and no new CEL is coming on? I just tried this tonight to see if my turbo would work, I cannot really tell if the turbo is working, I also just cleaned out the intake (which was not clogged), the car seems to be driving fine, struggles up hills, I am going to test it out tomorrow afternoon on a big hill, hopefully I will be able to tell if the turbo is working then. The CEL code I was getting before I tried switching the vaccum lines was p1556.
Any suggestions?

 

[aydn]

I put a DIGI-Z tuning box on my ALH and the limp mode went away.

 

[BIGTOMT]

Thanks for all the great posts here. I followed the links and I determined that my turbo is indeed stuck. I am 1500 miles from home so I will drive home in limp mode more or less and get it fixed there.
Thanks again

 

[Bdpprocessors]

99.5 A4 Jetta no boost. Started very intermittant then slowly advanced until all the time. Read post, swapped relays (?) at N75 - inside black box next to airbox on driver's side firewall - two small gray boxes that say "53" on them. That seems to have fixed the problem. (more testing tomorrow)So now which one is the bad one? Inboard or outboard or just buy two new ones? And how long can I drive with the swapped parts until new ones arrive?

I love this place!

You have two "53" relays??? i can only find one in my jetta is hooked up to the furthest left spot on the pannel nothing on the two spots furthest to the right..... could you take a picture of where they are?

 

[veedubber]

The check valve # 7 [beginning of limp mode post]go bad in time so remove and replace with new vaccum hose only. The valve is not needed, but if you feel better running one then just install a new check valve as they plug up for some strange reason causing big problems or become part blocked. With the old check valve off blow through it and you will see how restrictive the old one is and maybe plugged. A new one is very restrictive even. On my old 2001 that I gave to one of my kids, the check which was part blocked has been removed all together and replaced with new vaccum hose only. The check valve just may be the problem for most out here even if they are partly plugged. It may have been talked about, but to read all on this posting would take for ever so my 2 cents or 1

This ^^is the issue with my car, throws code and no turbo
clean out the gunk and it works again
sometimes even the little plastic tees inline will clog
Is it really OK to bypass the valve?
Where will the carbon that builds up in there go next?

 

[pbdr]

So where is this check valve #7? In the vacuum diagram, is it one of the joints of two vacuum hoses marked #7? And it's not the N75? Just trying to clarify.

Thanks.

Phil

 

[DelCoPA]

replacing the MAF on my '01 ALH and looking to improve performance. is there a difference between the Bosch and the Pierburg?

 

[ymz]

replacing the MAF on my '01 ALH and looking to improve performance. is there a difference between the Bosch and the Pierburg?

Are you sure you're looking up the correct replacements?

There IS a Pierburg replacement element for the ALH MAFs (Pierburg part number 7.22684.08.0) but it's not commonly available except by one or two specialist suppliers or on eBay (or from Europe)... In any case, if you're able to get one, you'll find that it's only the sensor element and you'll have to fight with the security Torx bits to remove the old element in your MAFs housing... They used to have a reputation as being bulletproof and much less likely to burn out than the Bosch units, but I found out otherwise...

Metalmanparts has the Bosch for $95 shipped, so unless you can find a Pierburg for much less than that, you may wish to avoid the hassle...

All the best,

Yuri

 

[dan kerkstra]

diagnostic codes

where do I find what they are there from the 2002 vw bug I just bought engine codes 17654,17964, 17987 auto trans code 529 any help

 

[ymz]

where do I find what they are there from the 2002 vw bug I just bought engine codes 17654,17964, 17987 auto trans code 529 any help

If you Google those codes you'll find your way to Bentley Publications and the code reference... it shows:

17654 Needle Lift Sensor Circ. Range/Performance
17964 Charge Pressure Contr. Negative Deviation
17987 Idle Speed Contr.Throttle Pos. Adaptation not started

Can't help with the auto transmission, but the VW offerings in that vintage are not known for durability... (many people convert them to 5-speed manuals...)

Have you had the car looked over by someone who knows TDIs?? The only specialists in your region that are known around here are down in Dallas... (there are 3 good ones there...)

I hope you didn't buy a money-pit...

All the best,

Yuri

 

[C15H32]

I would like opinions in my situation. I have been experiencing the following code for some time:
16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)
P0234 - 35-10 - - - Intermittent

I have went through the following:

• Checked MAF - ok
• Vacuum Leaks - ok
• Faulty N75 solenoid
  • The actuator does not move during key on, only when I start the car. Does this single out the solenoid to be the root cause?
  • I attempt to go to move the actuator via Vag-com, but I am not confident that I am on the right page. First I go to the '01 Engine', then to the 'Login - 11', which requires the password of 12233 to login. Is this what is meant to be 'Group 11' on the original email?
• Faulty Actuator
  • Holds 20in of Hg.
  • Mine actuator starts moving at 10in of Hg, not the 3-5 that was mentioned in the first post. Once it starts moving it jerks 1/4" within 1in of Hg. If anything this seems to be reduce boost according to prior responses.

Should I replace the N75? I stopped at the 'Sticking turbo vanes'. Any help or comments are helpful.

 

[commanderjjones]

Wow.....good info' (and a lot of it). I'll cast my vote that this should be a sticky. Obviously many members have this issue.

 

[nadroba]

I used to have intermittent limp mode. Tried a lot of things and someday I decided to replace the oem hose clamps on the intake for those easy found at any hardware store. The ones with a screw. Limp mode disappeared forever!!!

 

[commanderjjones]

My turbo isn't working....it was intermittent but quickly changed to not at all. I've read, re-read, tested, replaced all vacuum lines, and tested some more per this thread. With the engine on, I have plenty of vacuum (20hg) on the line going to the turbo and it will hold vacuum after the engine is shut off, but the actuator will not hold vacuum when I hook the pump up to it....I mean none at all. I can pump the vacuum until my forearm is worn out, but get nothing. This means that I have a bad actuator (hole rusted in it?), right? Just wanna get some feedback from the pros before I start throwing parts at it.

Assuming that is the problem, where is the best place to get one? I remember reading in here that they were available separately from the turbo, but really don't wanna read back through the 21 pages of this thread to find where. I've already read this so many times that I should have it memorized by now.

 

[flydope71]

Easy item to check

I found I had lost vacuum on one of the relays behind air filter on beetle. Found item #7 on the first post pics was plugged. Just sprayed some cleaner into the plugged part and replaced. Works like new and my codes stayed clear after resetting with OBDII scantool. My original problem was intermittent but gradually was limp all the time. Fixed for sure this time thanks to the info on this site.

Thanks


Did you try switching the two top lines on the two relays behind air cleaner? When I did the switch, I had full turbo power. This is what pointed to the screen or check valve... Whatever it is.

 

[ymz]

Limp Mode only during the day

This is somehow temperature related...

I finally got to take a trip in my wife's car during the day... after about 45 minutes or so, the car would start going into limp mode - usually while on the cruise control at about 65 mph... as the trip continued, it got worse - until recycling it would not help at the very end... The trip back, at night, was flawless... whether on cruise or driving in a "spirited" manner, the car wouldn't go into limp mode...

ALH motor, 428000 miles, turbo actuator recently replaced - adjusted properly (and behaving properly - at night...) The error code is 16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition).

Where to start, since this only happens during the day?

Yuri