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Drove from Phoenix to San Diego 2 months ago with AC on high the whole way. Right before getting into SD, driving up from below sea level to over 4000 feet, right before getting to the top of mountain, turbo cut off. I lost like 40-60 % of my power. Was cruising between 80-85 MPH the whole way.

This is the first time this has happened. Got home, used can air to blow out the connection on the MAF, Cleaned MAF with Cleaner spray, let dry and changed the oil. Took the car out, back to normal.So I figured car went into Limp Mode from something overheating ect. But no CEL or fualt codes stored.

Drove out to Phoenix and back again 1 week ago, no issues. 2 Days later while taking my lunch brake at work, I noticed turbo felt like it had no boost. Let the car cool down, drove home from work, no boost. Drove again the next day to work, cycled the ignition over and over, still no full boost.

Had my wife cycle the ignition while I was underneath the car to see if the Actuator was cycling/moving, no movement what so ever. Did a simple Vag-com scan, no fault codes. Unplugged the MAF just to rule that out, no change in turbo boost. I do not have a boost gauge, but the turbo is not whistling like it normally does.

So I either have a bad N75 or Bad Actuator. I don't have a vacuum pump to test vacuums, but will try and pick that up today and hook it up to the hose going into the actuator and see if its rusted stuck. I did lubricate the actuator and manually moved it back and forth, took the car for a spin, still no change.

Car still runs fine, I can drive to 80-85MPH on flat, 70MPH on hills max. It is hard to get to red line in gear. No smoke. Also have Vag-Com that I have done an Auto Scan but no Fault code come up, don't know much about using the software yet.....

Could also be a bad hose, but my gut felling says Actuator or N75. Stock Turbo, Stock Hoses and N75 ect. I do not think car is going into Limp Mode, No fault codes show when scanning Engine when off.

Car is tuned, and when turbo was working normal and driving hard, I blew some black smoke which is normal on my setup, now with the loss of power, no smoke at all. Just wanted to include that.

I also removed the N75, and tested with 12V and some wire, and I do get a clicking sound response from inside, so it seems to be working just fine.

I did noticed when moving the actuator it was pretty hard to get it to move back and forth. How much pressure do you need to apply with your finger to get it to move downward when underneath the vehicle? Also, I blew air in the inlets off all 3 areas on the N75, and it seems to not blocked my any means, some inlets I hear the same noise when I connect 12v to the connector. Normal for N75, but not normal for Actuator?

Since I have a tune and upgraded injectors and blow a little more soot, (I know, I need to get my injectors balanced too) could the soot (black smoke) be clogging my turbo up? I run the car hard, and normally shift over 3K daily to work and back home. Ordered a Mightyvac to test the Actuator next week. Mightyvac will be here by 7th, will update if I need to replace the Actuator.

I tried the Italian tune today. Ran hard high RPMS, nothing. Tried again after lunch, Got my first CEL on 3rd day, low boost to turbo.

VAG-COM Version: Release 409.1-US

Control Module Part Number: 038 906 012 BD
Component and/or Version: 1,9l R4 EDC G520SG 2507
Software Coding: 00002
Work Shop Code: WSC 00066
1 Fault Found:
17964 - Charge Pressure Control: Negative Deviation
P1556 - 35-10 - - - Intermittent

Took the Actuator off. Seems to be in good shape, but is very hard to move the rod back and forth. I ordered a new one today, 2 day air. I figure this stock turbo had almost 200K on it on stock actuator, might as well replace it.

The lever on the turbo that controls the movement of the vanes moves very easy and freely now that I took the Actuator off. So that's a good sign! No issues with sticky vanes. N75 connected to a 12v shows it works properly. But no Vacuum test on hoses till I get my mightyvac. I should have this car back running like she should by the end of the week. Will keep ya posted, any tips would greatly be appreciated!



 

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VW's have used metric spanners for many years so I don't think your 7/8" AF will be a lot of use. Yes some sizes are interchangeable. ;)
 

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Your nozzles and tune shouldn't cause any problems. Lugging the engine + high altitude can cause the turbo to fail due to compressor stall. Long story short, the thin air causes the turbine blades to no longer work and it can hit the housing or break the shaft. It's rare but it happens. Lugging the engine in general is also bad because there's less oil pressure.

The VNT actuator should move freely in 1 direction and hard in the other due to the spring in the can. You said it moves hard in both directions, that means it's bad. Please post a follow up to confirm that it solved the problem!
 

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Discussion Starter #5
VW's have used metric spanners for many years so I don't think your 7/8" AF will be a lot of use. Yes some sizes are interchangeable. ;)
I was only using it for leverage :)
 

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The VNT actuator should move freely in 1 direction and hard in the other due to the spring in the can. You said it moves hard in both directions, that means it's bad. Please post a follow up to confirm that it solved the problem!
Thanks for the info. Correction, actuator rod pushed towards diaphram is hard, when released, it springs back just fine. But have not connected vacuum to see if it off on pressure or if rod pops or shows resistance. Hope to be able to do that in the next few days.
 

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Discussion Starter #7
I had s similar problem turned out to be a boost leak at my intercooler from the turbo
I will check these too, if there was a leak or crack, I should hear a hissing sound right?
 

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I will check these too, if there was a leak or crack, I should hear a hissing sound right?
Probably not over the sound of the engine. Look through the FAQ section for the boost leak test. Long story short, pressurize the intake and it'll reveal any small leaks. Sometimes leaks only show up under boost as well.
 

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Got my mightyvac today. It took 22-23 HG to fully depress the actuator rod. It also begins to move as soon as I begin to pump from zero HG. So now I am not completely convinced that the Actuator is bad. It may be requesting more vacuum then normal, but I would think it would have some kind of range of boost to turbo while driving. When driving, it feels like boost in constantly stuck in low boost in one position. But vanes are not stuck. I might swap the n75 with the egr one and see if that's the problem.

I will start testing hoses and what not tomm. night and post a report. What do you guys think so far from the vacuum test off the Actuator?
 

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Probably not over the sound of the engine. Look through the FAQ section for the boost leak test. Long story short, pressurize the intake and it'll reveal any small leaks. Sometimes leaks only show up under boost as well.
I'm wondering if my mightyvac can connect to the intercooler for testing?
 

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Replaced Actuator with genuine Garrett. Made no difference after test driving car, still has CEL that I did not clear, so unless the car is in limp mode, I dont think this solved the problem. I did notice some hoses where in bad shape, and have not fully tested the n75.

The new actuator fully decompressed with less pressure then the stock one. So I thought that was it. Will clear CEL codes in the am, and test to see if car was still in limp mode. Still going to order new hoses to replace old ones anyways since the car has close to 200K. Also going to check for a possible boost leak or hose leak.
 

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My car does not go into limp mode unless I can't tell the difference which is possible since my turbo seems to be stuck in low boost or none. I can drive 60 miles to work, hit 90 mph today, but no power up hill, no passing power, slow pickup even on flat road, and I get no CEL! If I floor the pedal long enough I will eventually get one most likely becuase request and actual boost are off for a certain time or parameter of some kind.

Going to began with all hoses off n75!


Cleared codes this morning before my drive to work to elimante limp made no difference. Going to do some further test tommorrow(day off :)) Will be swapping egr and n75 valves to see if it's a bad n75. I will also turn the car on with boost hose from n75 unplugged and connect to mightyvac to see if the turbo reacts, and to test the hose itself. Also will check vacuum pump and hoses ect. Also ordered all new hoses, wbi be here Monday. Wish me luck!
 

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Problem Solved! :)




So after replacing the Actuator, that did nothing, but might improve and increase some boost and more responsive once I get vacuum to it back to par.

Woke up this am, started right on the car with a clear mind and already focused on testing specific areas on the car. Took the boost hose off N75, connected to to a mightyvac. Started the car, and got out and worked the turbo actuator by hand pumping mightyvac, and Actuator was moving properly and turbo worked. So that hose was fine.

Then I studied the hose diagram, and started at the vacuum pump and work my way all the way to the N75. First small hose I removed off the check valve two way splitter off the main vacuum pump hose or 10 on diagram below......



Or a picture off my car....



Bam, inside the nipple was some kind of solid fossilized oil that was acting like a ball valve one way (check valve) like the ball in this picture would be the peice of something clogging the nipple connection to hose pathway.



Connected the hose back up, took the car for a spin. Turbo is back to boosting and pushing out black smoke when I stomp on it again! Only problem now is that the turbo starts to whined up more towards the higher part of the RPMS. More in the 3K area instead of where it used to starting whining up at around 2100 rpms. So I am going to adjust the Actuator some, and map the block and see how close the actual boost and requested boost are off and try and get it tuned back where I like it.

Anyways, hope this article helps some one out there.
 

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Adjusted the Actuator 1 1/2 turn, done. Slight faster boost then before issue, great response. Will Graph and post later. Im a happy camper now! And my new hoses came in, and installed! I alwys blow some black smoke, but yet, at first when i opened her up, there was more smoke then normal. Now she can turbine!
 

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Great find! Do you mind if I add those pics to the troubleshooting articles!

Also, is that a circlip taped to the garret actuator box? It either looks strange or is it the tape that makes it look weird?
 
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