N75 Question

[GreenLantern_TDI]

Well scrambled your not alone in this issue. Im glad your still pursuing a fix, i gave up as mine f@#ked the fight outa me. I just drive it and turn the radio up louder as more noises appear. My car needs new tires, wheels, atleast 2 wheel bearings, some suspension bushings and a timing belt soon. Looking like about $3000 in repairs. Then the loss of power issue.... Ive given up. Car wins. VW 1 Me 0.

If you can get this issue resolved it might help get alota guys off the ledge so were all wishin ya luck.

 

[scrambld]

Well scrambled your not alone in this issue. Im glad your still pursuing a fix, i gave up as mine f@#ked the fight outa me..

HaHa...I've given up so many times.......but I just can't let it go. It's one of those things...changes you make and you want to experience the result...and I hope this ain't it...LOL

I've got a few suspension clunks....which I am pretty sure I have one bad front strut mount and one bad rear shock mount by the sound of it...and they're not that old either!
I have some rusty front fenders I should address. But, really if something comes along...like newer Jetta TDI/6spd or a newer Passat TDi/6spd I just may take this as a lost battle as well.....

......but in the mean time, I want to find what is holding her back. And, I have a feeling it is the original issue that was never found....cause it runs the SAME as before. Grrrr!

PS. except the original issue also came with a few limp modes/no code/recycle key and all is well till next time scenario......so something was resolved.

 

[Nevada_TDI]

Vacuum Gauge

Nevada, it would be no problem to get one, it's a required tool to have in the garage anyway.....

And, as mentioned above, I'll get injector deviation checked. My understanding if one (injector) is weak the ECU "weakens" the remaining injectors to provide for a smooth idle?

Would I "T" into the vac line going to turbo from the N75 and monitor what the vac is doing as I drive (or someone drives )? I have actually been thinking it would be nice to have a boost gauge right about now....to see if it is actually making any boost....but per my guru requested follows along pretty well w/actual boost so...? I can't believe how much stronger she ran before. My local guru says the BW turbo must have been stuck giving me max boost all the time. I can't swallow that because with the new PD140/tune/3 bar it was supposed to make more boost than the original BW turbo....? BUT, otherwise the car runs and drives perfect as a cummuter.

I would like my clutch to get the workout it deserves....

PS: When the shop checked...Mity-Vac at the actuator it began to move at 4mmhg and stopped at about 18 as I recall. But that doesn't tell me "when" the ECU commands it to move...correct? We did adjust the stop screw (read +/- on that one) and got the Mbar spread from 120 to 80...group 11 and I think that adjusts the vane position?

MAF unplugged, car runs NO different. I replaced it....as I've read it defaults to a "limp" home tune?.....car runs the SAME. Do I have an issue with MAP

I apologize as I don't have the knowledge most, if not all of you have on this board. I also realize the importance of having a Vag-Com to run logs and post screen shots. The best I can do is have the shop do it and email the shots to me....when their time permits.

I have been thinking about this, and there are lot of great ideas/solutions that have been given by people with much more experience and technical knowledge than I have and frankly, I am stumped myself.
You know the actuator works when you Mity-Vac it, so it is not the actuator.
With that said, you need to know how much vacuum you have and where you do and don't have it. Once upon a time my Jetta went from hero to zero and it was vacuum related; that was many years ago. I had 22" at the pump outlet and I had 6" or so at the passenger side of the car at a broken solenoid...
First thing, pull the check valve out and make sure it only passes air(vacuum) one direction.

EDIT: This should say vacuum gauges: They are $15.00 or less at Summit Racing. Generic will do just fine, I picked up two of them for 5.00 each a while back.

Put the gauge at the nipple that goes into the vacuum pump with nothing else connected and if you have at least 22" you can move on-- 25" is actually preferred.
On the vacuum side of the N75 put in a tee and check the vacuum reading at idle (22" at least) open the throttle and see if the vacuum changes up or down, hopefully it does not. Now move the tee to the turbo side of the N75 and check the vacuum both at idle and at partial throttle or if on the road at WOT.
To be honest, I am hoping you don't have full vacuum available. I have to go I will finish this post later.

*I'm back; If you don't have proper vacuum that would a long way toward resolving your issues. As had been said before the TDI engine works on kind of a closed-loop system. The throttle requests power, so boost is added, and fuel is added, and then the N75 is told to start cutting back on the vacuum, etc., etc. This is an over simplified explanation but I am sure you get the idea.

So the first thing is to be sure beyond doubt the turbo is getting the vacuum needed to spool.
If there is vacuum at the turbo then the problem is deeper...

This may not be the answer to your problems, but I thought since you appear to have tried everything else I would put it out there.




If you have solid vacuum you should now go as far toward the passenger side of the car and check vacuum at each of the solenoids

 

[Nevada_TDI]

Scrambld, have you found a solution or the source of the problem yet?

 

[boertje]

Exactly. I'm glad you brought this up. As I read through this thread and having myself dealt with a similar issue with bad N75 valve, I also had only 14" of vacuum. The nipple was so loose and was leaking that much causing the symptoms the OP has. Now with the pump repaired I once again have 25" Hg and all is well.

I have been thinking about this, and there are lot of great ideas/solutions that have been given by people with much more experience and technical knowledge than I have and frankly, I am stumped myself.
You know the actuator works when you Mity-Vac it, so it is not the actuator.
With that said, you need to know how much vacuum you have and where you do and don't have it. Once upon a time my Jetta went from hero to zero and it was vacuum related; that was many years ago. I had 22" at the pump outlet and I had 6" or so at the passenger side of the car at a broken solenoid...
First thing, pull the check valve out and make sure it only passes air(vacuum) one direction.

EDIT: This should say vacuum gauges: They are $15.00 or less at Summit Racing. Generic will do just fine, I picked up two of them for 5.00 each a while back.

Put the gauge at the nipple that goes into the vacuum pump with nothing else connected and if you have at least 22" you can move on-- 25" is actually preferred.
On the vacuum side of the N75 put in a tee and check the vacuum reading at idle (22" at least) open the throttle and see if the vacuum changes up or down, hopefully it does not. Now move the tee to the turbo side of the N75 and check the vacuum both at idle and at partial throttle or if on the road at WOT.
To be honest, I am hoping you don't have full vacuum available. I have to go I will finish this post later.

*I'm back; If you don't have proper vacuum that would a long way toward resolving your issues. As had been said before the TDI engine works on kind of a closed-loop system. The throttle requests power, so boost is added, and fuel is added, and then the N75 is told to start cutting back on the vacuum, etc., etc. This is an over simplified explanation but I am sure you get the idea.

So the first thing is to be sure beyond doubt the turbo is getting the vacuum needed to spool.
If there is vacuum at the turbo then the problem is deeper...

This may not be the answer to your problems, but I thought since you appear to have tried everything else I would put it out there.




If you have solid vacuum you should now go as far toward the passenger side of the car and check vacuum at each of the solenoids

 

[scrambld]

Scrambld, have you found a solution or the source of the problem yet?

Sorry, no update yet...I've been busy with home remodel stuff. I will get on it ASAP.....

....I will go take a quick peak around the vac. pump for anything that seems "off".......

 

[scrambld]

...... similar issue with bad N75 valve, I also had only 14" of vacuum. The nipple was so loose and was leaking that much causing the symptoms the OP has. Now with the pump repaired I once again have 25" Hg and all is well.

Are you saying the nipple on the vac. pump was loose? Mine is loose but I don't know what "too" loose is with that nipple. I took a quick look at it tonight and I am able to spin it and wiggle it a bit. Is it threaded in where it should be tight or is it more a snap fit?

I will take a better look at it in the coming days and update my findings. Thanks again everyone.

 

[boertje]

It is crimped in and over time can loosen and leak. Put a vacuum gauge on the small plastic nipple (feeding the n75 and other stuff) of the tube feeding the brake booster and see what vacuum you have. Should be around ~25" Hg.
What I did on a number of those pumps is worry some grease resistent sealant into the nipple to pump seem and then re-peen or recrimp the nipple back in tight. I used a fitting socket for this. Be careful when doing this as it's easy to crack the pump nipple housing. So far I have had positive results.

 

[duke21]

What would you say is 21 or 22 inHg of vacuum @ tandem pump exit ok or should be 25?

 

[Digital Corpus]

What is you altitude, or current barometric reading? At my place, 982 mbar is standard pressure so 25 inHg is the same as 26 inHg at sea level or ~19 inHg at 7000'.

 

[duke21]

Hm i think around 100meter only above sea level.

 

[Vince Waldon]

What would you say is 21 or 22 inHg of vacuum @ tandem pump exit ok or should be 25?

You're fine, regardless of your altitude.

 

[Nevada_TDI]

I had a brain storm this morning that may resolve more than OP's issues. Soon after I installed my 17/56 I started having strange issues lack of boost, odd boost etc. After quite a bit of digging--and replacing my N75 to no avail, I was led to check fuse #34, it was blown and was not visible w/o actually pulling it out. At idle check voltage to N75, if voltage is not a solid 12v the fuse is blown and/or you have a shorted solenoid that blew the fuse killing the voltage to all of the vacuum solenoids. Unplug all but the N75 and replace the fuse, if your boost comes back you now know where to look to fix the problem.

 

[GreenLantern_TDI]

Ive got 25" hg at all spots during idle but only 14" hg on the turbo. Scrambled have you checked this? Anyone know proper numbers for this?

 

[scrambld]

Ive got 25" hg at all spots during idle but only 14" hg on the turbo. Scrambled have you checked this? Anyone know proper numbers for this?

I will be checking vac this coming Weds or Thurs...1st chance I may have time.

 

[Digital Corpus]

You're fine, regardless of your altitude.

Okay, fine I might be splitting hairs, but even oiled roughing pumps have limits to how far from absolute vacuum they'll pump. That and stating 25 inHg is relative too but it could matter if he was at 7000'


But I digress. For the comment about vacuum at the N75, are you measuring the port going to the actuator because unless the duty cycle is set for full vacuum, you'll get a partial one like you observed from that port.

 

[GreenLantern_TDI]

This was at idle in the garage. No idea of duty cycle but y would it be 14? Id assume it would be all or non since no boost was requested.
Cant wait to see what scrambled finds on his.

 

[Digital Corpus]

The [stock] tune can/will call for a partial amount as set by VAG for a mixture of engine noise, idle emissions, and initial response. A custom tune can be set similarly. The control map is 3D with injection quantity on one axis and RPM on the other, at least in MK IV's and MK III's, but I'd guess it's the similar for the latter models, which do provide vane position feedback too.

 

[scrambld]

Cant wait to see what scrambled finds on his.

GreenLan........I can't either if it was something so simple like this I will be all .....but on the other hand after being told to replace turbo (upgrade was my obvious choice) and then all the subsequent $ being put into it for diagnostics by known gurus I will be .....but if it performs like others have experienced (sootman) I will be all again and all will be good.

Ps. I know once it hits the surge at ~2000rpm's it is making more power because it was slipping the VR6 clutch which was fine the day before the PD140/tune install with the stock everything and Stg2 tune. It's just gutless under 2000rpm's...runs like a NA diesel (non-turbo). It will sometimes take me surprise and really scoot but it is so infrequent that I never catch if it happened under 2000rpm's? It used to be just off idle to redline was all power, 1st gear hole shots were worthless with tire spin and traction control banging around trying to control it....2nd gear takes offs was where it was at with just enough tire spin and it would put you back in the seat and you could carry it further before shifting. Now she has the power range of a gasser...coming alive at 2000rpm's...kind of makes for a small power window for a diesel wouldn't you say. Its "fun" drivability has simply gone away.

 

[GreenLantern_TDI]

GreenLan........I can't either if it was something so simple like this I will be all .....but on the other hand after being told to replace turbo (upgrade was my obvious choice) and then all the subsequent $ being put into it for diagnostics by known gurus I will be .....but if it performs like others have experienced (sootman) I will be all again and all will be good.

Ps. I know once it hits the surge at ~2000rpm's it is making more power because it was slipping the VR6 clutch which was fine the day before the PD140/tune install with the stock everything and Stg2 tune. It's just gutless under 2000rpm's...runs like a NA diesel (non-turbo). It will sometimes take me surprise and really scoot but it is so infrequent that I never catch if it happened under 2000rpm's? It used to be just off idle to redline was all power, 1st gear hole shots were worthless with tire spin and traction control banging around trying to control it....2nd gear takes offs was where it was at with just enough tire spin and it would put you back in the seat and you could carry it further before shifting. Now she has the power range of a gasser...coming alive at 2000rpm's...kind of makes for a small power window for a diesel wouldn't you say. Its "fun" drivability has simply gone away.

Exactly what im seeing and feeling......
I fear it maybe a PD140 thing.

 

[morpwr]

Slow under 2K

Any chance the engine misses at idle some?

 

[Nevada_TDI]

I made a quick and dirty drawing this morning of how to bypass everything except the N75 valve and don't know how to post it. I tried here but all I got was lines of code.

Help please.

 

[Digital Corpus]

I made a quick and dirty drawing this morning of how to bypass everything except the N75 valve and don't know how to post it. I tried here but all I got was lines of code.

Help please.

http://forums.tdiclub.com/showthread.php?t=207484

 

[ecodean]

scrambld, check your PM's.

 

[Nevada_TDI]

Posted Picture

http://forums.tdiclub.com/showthread.php?t=207484

I followed the links, thank you. It did post.

http://pics.tdiclub.com/showphoto.php?photo=118276&title=vacuum-hose-drawing&cat=533

EDIT: Voltage and vacuum issues in or out of the N75 applies to every TDI with a VNT AFAIK, but the fuse #34 only applied to the MKIV's; there has got to be a fuse somewhere in every model to run the vacuum system.

So to reiterate: if you have significantly less than 12 volts at the N75 and/or at the other vacuum related solenoids there is a problem, I just can't tell you which fuse to check if you don't have a MKIV.

 

[scrambld]

Any chance the engine misses at idle some?

No, it runs, idles, drives fine since the beginning of all this (1.5+ years ago) just gutless when you really want it. But I will pay specific attention to the idle quality.

 

[Digital Corpus]

I followed the links, thank you. It did post.

http://pics.tdiclub.com/showphoto.php?photo=118276&title=vacuum-hose-drawing&cat=533

EDIT: Voltage and vacuum issues in or out of the N75 applies to every TDI with a VNT AFAIK, but the fuse #34 only applied to the MKIV's; there has got to be a fuse somewhere in every model to run the vacuum system.

So to reiterate: if you have significantly less than 12 volts at the N75 and/or at the other vacuum related solenoids there is a problem, I just can't tell you which fuse to check if you don't have a MKIV.

Depending on the meter used, it will likely appear that 12 V is not present at the N75 solenoid. The voltage applied is a PWM signal with a frequency of 300 Hz, give or take, and a peak voltage of 12 V so on many meters you'll see less than that.

 

[scrambld]

Exactly what im seeing and feeling......
I fear it maybe a PD140 thing.

Very well could be as we all have our perception of "performance" improvements. I've read a few happy campers on here that have done the PD140 swap so..?

In addition, it has the same symptoms that it had when the "bad" turbo was diagnosed....quite possibly it's the same issue that has not been discovered yet?

I hope to get into personally by the end of this week. I'll let you all know what info I can come up with. Thxs!

 

[scrambld]

Depending on the meter used, it will likely appear that 12 V is not present at the N75 solenoid. The voltage applied is a PWM signal with a frequency of 300 Hz, give or take, and a peak voltage of 12 V so on many meters you'll see less than that.

Had a quick moment of time. Checked voltage with my Sears Multimeter #82008 in V(DC).

So given the above quote I am not sure if there is anything meaningful. Results with N75 unplugged and meter inserted into plug.

Results with key on engine off: 9V

Results with engine running at idle: 11.09V

EDIT:
I drove the car w/N75 unplugged....it was even doggier!

 

[Digital Corpus]

That sounds quite correct