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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old March 4th, 2018, 19:09   #31
Steve Addy
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Thanks again! I'm going to take a look at that line today. While I messed with things friday, I pulled the line from the n75 and blew some air through it to see the wg open. I swear the car had just a little better power in my travels up and down the mountain for errands. I'll have to grab some electronics cleaner today after church. This is the first I've read about any kind of cylinder issues in this car. I was blaming the oil on the ccv which I plan to reroute to keep thing cleaner

My n75 makes no noise at idle, Steve. I wish I had the vcds to cycle it, but I'm not spending that kind of coin.
Yep, try cleaning it and the hoses out and see what happens.

I know that there is a range in the volume for these N75 valves. I can hear the one on my Mk3 with the hood closed, not sure about that with the wagon but I do know I can hear it with the hood open.

Steve
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Last edited by Steve Addy; March 12th, 2018 at 11:48.
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Old March 6th, 2018, 13:30   #32
2006PSDSD
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That line from the n75 to the WG actuator was full of oil! I'll see how it runs after I get the ball joints and tie rod ends replaced. Stayed tuned
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Old March 6th, 2018, 16:36   #33
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oil in those lines is due from a few reasons, dirty air filter, too much CCV blow by at idle or other turbo oil issues.
i normally see a tiny bit drip down into the air box but it works fine. Point is, on a healthy stock car, change the air filter and fix your CCV if it continues if your turbo journal bearings are acting proper.
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Old March 7th, 2018, 05:30   #34
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It's fairly common for older 1Z and AHU cars to accumlate oil in the WG (vacuum) pressure lines over many miles - just a fact of life. too much oil can limit WG movement.

On mine, oil had also made it into the WG actuator on mine - ended up getting it out by removing the actuator from the turbo (PITA) and cycling it with the pressure port facing down. That cleaning and a new N75 cured my car of any intermittent limp issues.
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Old March 7th, 2018, 06:08   #35
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Dang it, I was hoping that was somewhat normal. The dirty AF is what causes the excessive CCV blow by I assume, or a malfunctioning breather maybe? I know the turbo was replaced by the original owner, so maybe 150k ago or so. Are they not a long lasting design?
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Old March 7th, 2018, 06:10   #36
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Thank you all for your help, I'm going to fix this thing...or sell it
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Old March 12th, 2018, 04:26   #37
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The car ran like a top this morning! I cleaned the N75 and the vac line to the WG and walla!

The valve was plugged with something I didn't see but I got that burst of pressure out the other side when it broke loose. The vac line didn't have much for oil in it, but it was enough to cause a restriction. I assume this is why the limp mode only happened when it was <20*F outside
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Old March 12th, 2018, 05:30   #38
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Glad you got it fixed.
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Old March 12th, 2018, 11:47   #39
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The car ran like a top this morning! I cleaned the N75 and the vac line to the WG and walla!

The valve was plugged with something I didn't see but I got that burst of pressure out the other side when it broke loose. The vac line didn't have much for oil in it, but it was enough to cause a restriction. I assume this is why the limp mode only happened when it was <20*F outside
A successful fix is always a satisfying outcome! Glad to hear that you're back with consistent power (or at least we hope you are).

I'm curious now as to whether you can hear your N75 clicking when the car is sitting and idling with the hood open?

Steve
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Old March 12th, 2018, 12:14   #40
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I'll listen for the clicking when I get home tonight, Steve
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Old March 19th, 2018, 06:50   #41
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My N75 valve clicks like you said yours does, Steve. I guess cleaning that line and the valve got it working again, but I still have the limp mode thing, it's not nearly as predictable
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Old March 19th, 2018, 08:03   #42
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I cleaned my N75, got the same results - it got better, but still had limp intermittently.

Replacement cured mine, also made my boost oscillations go away - I just chalked it up to the old valve not being able to move as fast as a new one.

Slowly shorting windings maybe?
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Old March 20th, 2018, 04:45   #43
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I was planning to just replace the silicone hose, thinking that it may be partially blocked because I didn't feel like brake clean and silicone would get along for cleaning it good. I just used WD40 and some shop air. Just to be done with it, I'll replace the N75 and the hose. Fingers crossed that does the trick!

I wonder what these people on the highway think when they see my car go totally black when I cycle the ignition to reset the limp mode, LOL. I live in the mountains and travel in pitch dark mornings at 4am

I was going to order the valve from IDparts. Is that a good source? It's 45 dollars, not the recommended 75, that's why I'm asking https://www.idparts.com/ahu-1z-n75-v...83f-p-451.html
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Old March 21st, 2018, 12:34   #44
Steve Addy
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That's the correct valve.

Steve
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Old April 2nd, 2018, 04:36   #45
2006PSDSD
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I installed the valve and new vac line last week and have about 200 miles of zero limp mode! I think that valve may have been fine after I cleaned it last time, but that vac line was preventing the system from working as it's designed because of the oil in it. I believe that the cold temps when LM would mostly occur were caused by the oil viscosity and it not moving freely enough to actuate the WG on a normal basis. When I took the vac line off it had 5 half dollar sized oil drips on the floor. For a 3mm line, that's quite a bit.

Thanks for everybody's help!
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