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

i was just wondering on here, has anyone else had a creaking noise issue when taking off from a stop or when stopping? almost sounds like the frame of the car is stretching. trying to find out if this might be related to the turbo problem that we are having.

rdkern said:

Quite a bit of resistance. Thumb-hurting resistance. Better if you use a mity-vac to apply the vacuum - that way you're testing the whole actuator, not just the veins.

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If the turbo vanes are stuck, can you move the actuator arm at all?

Rhh said:

Thanks for the reply....

Yes, one hose at a time,

The routing is exact as per the diagram in the thread (same one in my OEM shop manual)

The hoses are all secure and fit well.

I checked the n75 and actuator hoses and all of them are connected properly.

I just pulled the exhaust pipe off of the left side of the turbo to test the shaft for any play (there is no play, and there is also smooth free movement of the turbine blades).

I've heard that worn bearings can result in the shaft wearing out and oil leaking into the turbines, (I assume just on the intake side?). I took pictures of both sides of the turbo, the exhaust side is free of oil but the side feeding to the intake appears to have oil on the outside of the hoses. I'm not sure where it comes from.

Can anyone tell me if this is a sign of an internal oil leak within a turbo. There is oil above (gravity) these hoses and I assume the leak was the same vacuum pump oil leak I fixed previously. (The exhaust side of the turbo is better sheltered in its location and didn't get leaked on???)

Thanks again.
Rob

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You're going to have SOME oil on the intake side. If crankcase oil levels are holding up OK (folks seem to suggest up to a max of 1 qt per 10k miles [sorry, you'll have to do the conversion to metrics]) then your turbo seals can't be bad. If there's oil loss then there's other things that can help the oil disappear, not just the turbo.

If your actuator moves freely (which in turn moves the turbo's vanes freely), and assuming there's really no mechanical damage to the turbo (I'm thinking that you'd know of such), then you need to further scrutinize the vacuum side of things. There's a plastic "T" that can get blocked up and cause people all sorts of fits. Make sure that all the fittings and such are going in the right places and are oriented correctly (refer to the vac line pictures).

Another simple and quick test would be to watch the actuator as the car is started. If it doesn't open up (and then close), and we know there's no mechanical issue, then it's a control issue (vacuum or ECU).

I had a similiar problem. just changed the fuel filter.

If the turbo vanes are stuck, can you move the actuator arm at all?

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Try to move the acuator rod by hand. If you can't move it, the vanes are stuck.
The only solution that'll last is to strip it and clean it out.An ultrasonic cleaner bath also helps if you can find one big enough to dunk it in.

Thanks everyone....

First a thanks that I should have posted at the beginning. Thanks to CG for this thread. Thanks to all the replies and those who take their time to help out strangers.

Also Thanks to those replying to my questions.


Here's where I'm at if anyone has the patience to help further???????


To add to my "done"list:

-replaced the n75.....

Woooohoooo got about a full day or two of 95% what I'm used to power.

Then back to NO TURBO AT ALL....sigh.

So I,

-replaced fuel filter (no change in limp issue)

-replaced some worn wiring to the n239 (behind intake manifold) that was giving me a fault code "open to ground...intermittent" (no change in limp issue)

-removed air routing hoses to inter cooler and no pooling oil or signs of a shot turbo

-physically moved actuator arm....free movement, not stuck at all

-hooked up the VCDS and attempted to cycle actuator (using test block 011 for the n75 per this thread...way back)
There was no actuator movement at all. The computer showed the cycling of the n75 but nothing happened on the car.

I checked the vacuum lines again, all are intact, properly routed,

I hooked up,an old vacuum gauge to measure the vacuum out of the system, at idle it builds up to 30 or so out of the main line (the soft line leading off of the main trunk to the brake booster), but measured off of the n75.... Nothing.

I assume this means a leak or loss of vacuum but I can't for the life of me find out where. I HAVE CHECKED THE ENTIRE SYSTEM.

Failing any help here can someone suggest a reliable tdi guru in the Vancouver/Fraser valley area ???

Thanks again!

Since it ran fine for a day, the check valve apparently isn't in backwards, but I would check it anyway to be sure.

If you have zero vacuum at the N75, then the leak must be pretty bad and I would bet that just blowing on the hoses with your mouth would be enough to find the leak.

Thanks so much. I'll try that today.

Check valve should be white side toward the n75 according to my shop manual.... is this correct?

I confirmed the check valve is in place and I routed the vacuum directly from the large brake booster hose into the top of the N 75. The car runs like a rocket.

The leak seems to be elsewhere outside of the N75 circuit ...Is it possible for the EGR valve itself to have a leak internally? If so how does one go about diagnosing this?

I'm not sure if this still counts as limp mode since it seems to be a vacuum leak issue.

So that I don't hijack this thread anymore with my nonsense can anyone suggest a better place to post?

Thanks again!!

TDI 101 would work. Be sure to sum up what you have done here or at least link to it.

Just a reminder for folks chasing it... After all my chasing and money spent on replace all the basics, mine ended up being a bad ECU.... Known good Used ECU and NO MORE limp mode.

Fanatastic write up Mr Grizzly. This is exactly what i needed. Thank You!

I'm definitely going to share my findings.

Cleaning intake manifold

I've been told by a reliable VW mechanic that my intakes are clogged. To clean them is a bit complicated for a simple mechanic like me. "They want about $445 for the job. Part of that is for sending the manifold to a special environmentally licensed place. But, I could probably do it with some instruction and time. I've worked on motorcycles mostly with some car repairs. I wouldn't attempt it until spring as I don't have a heated garage, but, any information or advice would be healthful. It's a 2004 Jetta TDI with a standard tranny. The engine has 360,000 miles on it and was overhauled early this year.

>>I don't think I asked this in the right place. Going to post to TDI 101

hwblake said:

I've been told by a reliable VW mechanic that my intakes are clogged. To clean them is a bit complicated for a simple mechanic like me. "They want about $445 for the job. Part of that is for sending the manifold to a special environmentally licensed place. But, I could probably do it with some instruction and time. I've worked on motorcycles mostly with some car repairs. I wouldn't attempt it until spring as I don't have a heated garage, but, any information or advice would be healthful. It's a 2004 Jetta TDI with a standard tranny. The engine has 360,000 miles on it and was overhauled early this year.

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I don't see the BEW having as many problems with intake clogging. you might take out the EGR valve on the front of the intake and take a look, a small amount of soot is normal, however if it starts getting down to the size of a dime, then it's usually time to remove and clean it

never try to clean it on the engine... always remove it to clean it.

if yours was a 2003 or earlier, I wouldn't be skeptical.

alphaseinor said:

I don't see the BEW having as many problems with intake clogging. you might take out the EGR valve on the front of the intake and take a look, a small amount of soot is normal, however if it starts getting down to the size of a dime, then it's usually time to remove and clean it
never try to clean it on the engine... always remove it to clean it.
if yours was a 2003 or earlier, I wouldn't be skeptical.

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What he said. Three 5MM allen screws and the EGR valve comes right out and you can see for yourself what is going on.

Seems like it's been a long time since this thread was written but I wanted to mention my recent experience with my 2001 TDI Jetta. I had the intermittent loss of power and tried cleaning the maf first with tuner cleaner. Seemed to help but the problem returned. Took the advice herein and replaced the maf. Seemed to help but the problem returned.
Then my neighbor mapped the car and found 'intermittent voltage from maf.' I tore the end off of a business card, folded it over and wedged it across the top of the oval maf connector and shoved it together a week ago. The loss of power no longer happens and the car has more torque than it did before all of this. It screams.
Now, I have an airbag light on and see that, again, it's probably the under seat connector...
I recall my '83 mercedes diesel had all sorts of connector problems. Plate lights, brakes, starting circuitry...

Help withturbo vcds

Hello all, I'm posting here in hopes of reaching members who have also gone through the overboost troubleshooting and may be willing to give me some pointers. Thanks Canadian_Grizzly for getting this going and thanks in advance for anyone who can offer some guidance.

I had another thread going, but it kind of died out as I was getting some real data. Thanks to members that posted there.
http://forums.tdiclub.com/showthread.php?t=453323

I'm getting limp mode on a hill on the way to work pretty consistently. Trouble code is P1557, positive boost pressure deviation

From the OP, here was the sequence for troubleshooting

Bad Maf (Oxygen Sensor)
Leak in the vacuum system
Faulty N75
Bad actuator
Dirty gummed up turbo causing variable vanes to jam or stick

1. I unplugged the Maf and the car ran terribly all the time
2. I replaced every inch of vacuum line
3. Replaced the N75

As for bad actuator/turbo, honestly I'd most likely go the route of upgrading once if/when I'm convinced that is the issue. My goal now is to see if there is something else simple that I should check. Here are some VCDS graphs which only tell me that the system is poorly controlled. Maybe they tell others something more nuanced that hints at the underlying issue. Please note that I've graphed the relevant solenoid position on the right hand vertical scale. So, for example, you can see my N75% parked up near 95%. Now I'm *assuming* that high N75% means that the valve is opening the turbo actuator to atmosphere (rather than vacuum) in an attempt to reduce the 400mbar overboost. If that's not the case, then I'm really lost as to what the ECU is doing!

2002 VW JETTA 1.9L TDI turbo troubleshooting

First of all, thanks so much for the original post that provided the step by step tutorial. That is well done and the follow up support and instructions are great as well. Thanks to all the replies and those who take their time to help out strangers.
Basic facts...
Starting about 6 months ago I had an intermittent turbo boost and it gradually got worse. Still intermittent but working less frequently than a few months back. Using this tut, I unplugged the MAF sensor and the 'Limp' mode was still present, therefore i assumed that wasn't the problem. The check engine light had been on before so I don't know if that was caused by the MAF. (I'll come back to this step later)
The next thing I did was check on the vacuum lines. I found an obvious hole in line between part 4 and 13 in your diagram and replaced the line. The turbo instantly worked great for the next 36 hours. After it stopped working again I double checked that the lines were still connected. Perhaps I had multiple problems to begin with, so I sought out to find the problem once again.
Currently the turbo is hit or miss. If it is not working and I cycle the ignition at a stop light then sometimes it starts working again. Being mechanically savy but not really knowing turbos I've made some assumptions.
My assumptions with out acquiring a vacuum gauge or VAGCOM...
The N-75 valve is working because the turbo works great or not at all, seems something like that shouldn't be intermittent. The veins aren't stuck, the vacuum lines are okay (i'll double check).
My questions...
The test for the MAF sensor is to disconnect and see if the limp mode is "same or better". I believe the issue is electrical as opposed to mechanical or vacuum issue but I haven't used any testing equipment. Disconnecting the MAF sensor has no effect on turbo that I can see and the check engine light comes back on a >1min later. What's the likelihood of the problem being the sensor? With the ignition reseting and fixing the problem, what do you recommend as a more stringent test, or should I just buy one? Am I correct in assuming the problem is electrical because of how intermittent?
I'm willing to purchase a VAG-COM or take it in for service but I'd love to discover and learn the Turbo and fix it myself.
Tutorial that I've been following.
http://forums.tdiclub.com/showthread.php?t=179589
Thanks to one and all for the help.
Jacob Burger

Jacob,

You really do need to read those codes. You don't need to get a VCDS to do so, just one of those cheap ODBC-II readers will do the job but you need to see what the computer is complaining about. Also, is this the original turbo? How many miles on the car?

dilkie,
Thanks for the quick reply. I have ordered an OBD-II reader and it should be here in a couple days. This is the original turbo and the car has 187,000 miles. Thanks.

dilkie,
I received the BAFX ODB-II code reader and with Torque android app their were 3 codes. I don't believe the 2nd two are relevant but I'll include them just in case.

1st reads P0102 Powertrain - Mass or Volume Air Flow Circuit Low Input
2nd reads P0118 Powertrain - Engine Coolant Temperature Circuit High Input
3rd reads P1556 Powertrain - Tap for multiple. (Once clicked it has something to do with the cam shaft)

I have cleared the codes and driven for a 1/4mile so far and the turbo is working well. I will be driving to work which is a 1.5hour drive soon. So I'll see if the codes come back and will have a better understanding of how it's doing.

Should I replace the MAF or wait. Someone else suggested bad contacts on the MAF but my contacts are clean. Any input would be helpful. I'll reply with how well it does tonight with a longer drive. Thanks in advance.

It may not be the MAF, you seem to be walking down the same path as I did... The airflow can be low because the EGR valve is sticking open and slow to close. That happened to me after my car had sat for a while. Turbo lag was brutal and I replaced everything trying to fix it, MAF, MAP, all the vacuum hoses... I found out it was the EGR when, in desperation, I clamped off the vacuum hose to the EGR to prevent it from opening... worked wonders... 'course, then the computer throws a "airflow too high" reading because it expects to see a lower airflow when it commands the EGR to open (and it can't)...

With the age of yoiur car and the miles, you could very well be experiencing turbo issues. My first turbo failure was the same as yours, took about 6 months of working, then limp and I'd reset using the ignation key (I didn't bother to stop, just turned the car off and on while driving, yes, I'm dumb). Eventually it just stayed in limp... Also noticed more oil consumption around the same time... that oil, it turned out, was slowly filling up my intercooler (tip, drill a small hole in the bottom of the intercooler to prevent run-away and/or hydrolock)... I replaced the turbo, the vanes were totally stuck.... In my newer car, I did a turbo job myself a month ago (not for the faint of heart but educational). In that case the turbo failed catastrophically, the shaft snapped so the turbine was no longer connected to the compressor and it leaked oil into the intercooler very rapidly. Couldn't drive that one.. In both cases, the cars had ~300K (kms) on them so don't know if that's the expected life or not...

Good feedback, I'm still hopeful. During my 1.5hour commute yesterday I played with Torque diagnostics a bit and that original fail code came back that I though was not relevant. The P1556 Powertrain - Tap for multiple. Reads out as Charge Pressure Control Negative Deviation. Im curious if that P0102 Powertrain - Mass or Volume Air Flow Circuit Low Input, is fixed from the bad vacuum hose because that code has not come back. Its just weird that I can cycle the ignition at a stop light and get great boost for awhile, then it suddenly goes away. The Torque Boost readout shows 10-15 psi when it is working and then it just suddenly stops and will fluctuate between 0 and 1 psi. It seems like there is still a smoking gun here. I might try to replace that PCV. At this point Im guessing it is item 4 and 6 in the diagram below. Maybe I should clean the EGR? Thanks for any thoughts or info.


________________
'02 Jetta TDI 1.9l

Glad you're having fun... "Charge Pressure Control Negative Deviation" means that the computer asked for boost and didn't get what it asked for... That's what's leading to the limp mode eventually. After a few attempts of asking for boost, it decides there's something wrong and won't request any more boost, in a effort to save your engine from something serious (like over boost, which could cause serious damage)... Still pointing at the turbo, in my books, I'm not a mechanic mind you. But this is the same path I walked down... but it could also be the N75 valve (mounted on the firewall with the vacuum hoses going to it), since it's the beast that converts the computer's "give me more boast" electrical signal into vacuum to move the vane actuators... (number 6 in your diagram).. you can check that by substituting in the other valve (number 4), it does the same thing but for the EGR valve (just block off the vacuum line to prevent a leak)... Did you check to see if the vanes move freely? (PITA to get at, mind you).

So it finally stopped raining here on the east coast and I got under the car. Forgive my ignorance but #6 in the diagram seems to be up high in the engine compartment and #1 is down low near the firewall. Based on the fact that it should be hard to get to, I'm assuming that the N75 valve is #1? When checking if the vane actuator was sticky, are you talking about the part that comes from part #2 on the diagram? If so, that part does seem a little tough to press in with just my hands. It feels like I'm pressing towards the part #2 and away from the turbo as opposed to towards the turbo and away from the #2 part. (if that makes sense) Thanks for any guidance. Still weird that simple ignition cycle makes it work for awhile. I'm wondering if I should just replace the n75 and the n18 valves and see it that helps. Thoughts? Thanks in advance.

#1 and #2 are for the ASV mounted to the EGR valve on the top of the engine. What you need to do is follow #3 down to the turbo. This will be accessed from underneath the car, or, if you aren't Gigantor, you can reach it from the top. You can pull hose #3 off where it connects to #6 and use a Mityvac or some other tool to pull a vacuum while watching and/or feeling for smooth movement of the turbo actuator, then check to see if it holds vacuum. If it doesn't hold vacuum, then the actuator is shot. If it holds vacuum but the turbo actuator doesn't move, then the turbo vanes are seized.

If it moves the turbo actuator smoothly and holds vacuum, then you have a problem with the N75 circuit. It may not be getting vacuum, it may not be getting a signal or it may just be broke. It's a matter of elimination and I think that is spelled out in the original post of this thread.

Thanks, Whitedog. I'll get a Mityvac and try that.

2006 jetta tdi

If I sit lets say in parking lot waiting on somebody for a few minutes my jetta has no power it falls on its nose . But I can pull over turn off and let it sit a few minutes it is fine and yes check engine light is on

sparks011 said:

If I sit lets say in parking lot waiting on somebody for a few minutes my jetta has no power it falls on its nose . But I can pull over turn off and let it sit a few minutes it is fine and yes check engine light is on

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Well, you have a 2006 Jetta, so you have an A5 platform. This thread addresses the A4 platform, so your best bet is to look around in the A5 section. Also, stop by AutoZone or another parts store to get your codes read. They might tell part of the story.