Low power / Surging

[TonyJetta]

The Passat has been having a surge issue lately. In the spring, it felt more like it was temperature related. i.e. more surge in the cold mornings than in the warmer afternoons. Lately, it's been happening all the time, usually WOT in 3rd above 2700rpm. I don't have any VCDS logs, yet.

As I was driving home yesterday, the engine felt a little down on power; just enough to notice. So, I got home and proceeded to change the fuel filter. Or, so I thought.
Pulled the old fuel filter and proceeded to install my spare that has been rattling around the trunk for the last year (nearly 20k miles).
As I am priming the fuel filter with my mity vac, I notice an air leak, more accurately, a suction leak. No matter what hose I tightened, I could not get the leak to stop. I even loosened then tightened the water drain.

I'll try the T later, I just ran out of time, and had no interest in changing a fuel filter in the rain.

I'm thinking the surge may be a lazy N75...It has 4.5 years and ~80k miles.

I'll be ordering 3 fuel filters today. 1 for the car's immediate need, 1 for an in-car spare, and 1 for a spare at the house.

So, I had to run up to the local parts store at 8pm to replace the batteries in my truck. After 2.5 years they were starting to go. Turns out 1 had <10 CCA and the other was <12V. Fortunately they were 6mos inside the 3 year free replacement warranty. Nothing like changing batteries in the rain! Fortunately, the fellow behind the counter was helping, and seemed to know what he was doing. I'll be double checking everything this weekend.

More to come.

Tony

 

[TonyJetta]

I replaced the fuel filter today. Here's those details.

While I was in there, I replaced the air filter. The low power seems to be resolved. However, the surge now seems more like a flat spot at about 2700rpm in 3rd, WOT.

I think I'll just replace the N75; It's been in service for nearly 5 years and 80k miles.

Tony

 

[honda_vtec2]

I replaced the fuel filter today. Here's those details.

While I was in there, I replaced the air filter. The low power seems to be resolved. However, the surge now seems more like a flat spot at about 2700rpm in 3rd, WOT.

I think I'll just replace the N75; It's been in service for nearly 5 years and 80k miles.

Tony

Hey Tony, I experienced something similiar to your condition. I had a bit of fluttering idle and a small surge around 1800-2800rpm. I traced it down to the N75. I took out the N75 sprayed it with brake clean while i used an air compressor to try to blow out any crap in there. After that i soaked it in Varsol remover for about 30 minutes and then blew it out with the air comp again. Since then i've put about 5k on the car. I plan on replacing it when i drive down to the US next month (I will keep the new one as a spare in case this old one starts acting up). The old one has around 90k on it. So far it's clicking again and performing like new. I also used air hose with a cap and my fingers most times to try and isolate the fluid leaking out the port holes while i sprayed it.

Forgot to mention. I also placed 2 inline filters on the car. One from the airbox to the egr and another from the turbo actuator diaphragm to the N75. They were cheap filters and i hope that helps with the oil and grit that goes in there. They are the clear plastic ones, so i can see if they get plugged up or dirty. So far so good.....

 

[TonyJetta]

honda_vtec2,
Thanks for the info! That helps. If I get time this weekend, I'll clean out the N75 as you described.

Tony

 

[50harleyrider]

Tony,
I kept having thermostatic tee issues until I upgraded to an A4 one. It takes the longer A4 fuel filter but it's a straight swap and I figure more capacity is always better. Let us know when and how you get the surge out. That's a PIA issue always for these cars. A buddy of mine is an independent truck driver and he changes fuel filters every time he changes oil. He told me the quality of diesel fuel is really going to s*!t. I think he's right. When I run biodiesel upward of B60, mine seems to behave better too. this winter I plan not to go below B40 with winter additives.

 

[honda_vtec2]

honda_vtec2,
Thanks for the info! That helps. If I get time this weekend, I'll clean out the N75 as you described.

Tony

Tony, no probs. Just some issues i've come across and thought i'd mention them if it helps at you at all. I've learnt so much from guys like you on this club, so consider it a reminder to knowledge you already knew

I have a 2nd used n75 that i'm going to clean to see if it brings it back to life. so far it's boosting only to 9psi. After i cleaned it with Brake clean and Wd40. It went up to 11psi, not sustained. So i'll soak that guy and see if it helps it. Right now, i'm still happy that my current N75 is working like new again. for how long, not sure....LOL

 

[TonyJetta]

50harleyrider,
I was thinking I might have to replace the T, as well. But, once I replaced the filter with a new one, it primed in <5min with the mityvac. Not to mention, you could see the crack in the plastic water drain knob.

I've also had thought of installing a cat filter, instead of the OEM. I'm just not sure I want to eliminate the thermostatic T in the winter driving. Not that we get that cold for long in the winter around here.

Thanks fellas!

Tony

 

[ToddA1]

Winter in AZ? Whats the coldest you get there... 40°s? A filter for an early A2 diesel will get rid of that T.

I think I'm now in need of a N75. Off topic, but where do you guys mount gauges in these things? The factory left no open spots, and I'm not sure I want to do an A-pillar pod.

-Todd

 

[TonyJetta]

Winter in AZ? Whats the coldest you get there... 40°s? A filter for an early A2 diesel will get rid of that T.

We can have a few days into the 20's...commonly into the low 30's. I live at 3400ft elevation.

At any rate, the thermostatic T isn't leaking, so I'm not motivated to change...yet. I'm also watching the thread about using a Cat fuel filter with a generic mount/adapter.

Tony

 

[ToddA1]

Interesting, I wasn't aware that it gets that cold there. You're lowest is slightly higher than my high, here in NJ.

Anyhow, I have the A2 filter in my garage and may be installing it tomorrow. People in colder climates have reported no issues.

-Todd

 

[TonyJetta]

Todd,
Thanks for the info. I will keep it in mind.

Onto today's developments...
I was accelerating onto the freeway, doing my daily Italian tune up, when I hit limp mode about 3500rpm in 3rd gear. I suspect N75 has given up the ghost. Later in my commute, I floored it to 3krpm and hit limp mode again. I suspect the fact that it's about 70F this morning may be exacerbating the N75 issue. We will see how it runs at noon in 95F weather.

I'll pull the boost hoses of N75 to see if there's oil present. Last December when I had it all apart, there was no oil present, but that was with a different turbo. I'll also be checking the wiring; rodents abound!

Tony

 

[ToddA1]

3-35K was the same range where my car falls on its face. Yesterday, it happened and it never came out of limp mode. Haven't started the car today.

I ended up ordering a new N75, today. I've read a few people mention some type of filter before it, but I have no clue where to find a filter with tiny barbs.

-Todd

 

[TonyJetta]

3-35K was the same range where my car falls on its face. Yesterday, it happened and it never came out of limp mode. Haven't started the car today.

Key-off:Key-on resets it just fine for me. I don't even clutch it; just turn the key-off then back on.

I've read a few people mention some type of filter before it, but I have no clue where to find a filter with tiny barbs.

I, too, have read about this recently, but I have no details. If you find the detail, please post them! I will, likewise.

Tony

 

[TonyJetta]

The N75 control hoses do have some oil in them.

I had an issue with car while I was out at lunch. I was pushing it a little, trying to see if it will go into limp mode with warmer (90F) air. Yes, it does. It also stumbled, like it was running on 3 cylinders. Once I cycled the key, it cleared up. I'll have to wait until I get home before I can scan it to see what codes are set.

I'm starting to wonder if the injectors or pump needs to be replaced. The injectors are a set I bought from Frank 4 years ago. AFAIK, they were fresh at the time, albeit stock.

Tony

 

[50harleyrider]

Tony,
Once I got oil in the N75, I had to junk it. Putting solvents inside it is not the way to go-just replace it and the oily line and figure out why the line is getting oily and fix that.

 

[TonyJetta]

50harleyrider,
Thanks for the input. I never did scan the car last night. I will later today...thankfully, Fridays are short days.

Tony

 

[ToddA1]

Although I agree that harsh chemicals such as brake or carb cleaner may not be wise, contact cleaner or starter fluid should be fine. IIRC, MAF cleaner is just starter fluid.

The solvents in those are designed to flash off rapidly, leaving no residue. WD-40 shouldn't hurt anything, either. It's dielectric.

-Todd

 

[Abacus]

Solvents inside the N75 isn't an issue since it's just a metal shuttlecock inside a metal housing. It's a coil, so it magnetizes and moves the shuttlecock back and forth in a rapid movement, which is the clicking you're hearing. I took one apart years ago and had a look inside, they're very simple. The can get gummed up from stuff getting in them and you don't want them to have a residue when you're done because they'll 'stick' and not work right. Part of the problem is the coil part can get weak over time and it'll malfunction. I have had them last from two to 4 years, and the one I'm on right now is just over that.

If I can find the pictures I'll post them of what it looks like inside.

 

[TonyJetta]

Mark / Todd,
Thanks for the replies!

Tony

 

[50harleyrider]

Solvents inside the N75 isn't an issue since it's just a metal shuttlecock inside a metal housing. It's a coil, so it magnetizes and moves the shuttlecock back and forth in a rapid movement, which is the clicking you're hearing. I took one apart years ago and had a look inside, they're very simple. The can get gummed up from stuff getting in them and you don't want them to have a residue when you're done because they'll 'stick' and not work right. Part of the problem is the coil part can get weak over time and it'll malfunction. I have had them last from two to 4 years, and the one I'm on right now is just over that.

If I can find the pictures I'll post them of what it looks like inside.

Abacus, Do you know the metallurgy of the 'metal' components inside the N75? I think not so don't asssume any solvents won't hurt them. Ask one of the Gurus about this. I'm not a metallurgist but I am a mechanical engineer and know that introducing foreign substances inside a component not made to have them is not good practice. Tony, do what you think is best.

 

[Abacus]

I went to college for civil engineering and work as a chemist, so I know all about chemical comptability.

If it's not working to the point you need to clean it out, then give it a try, there is nothing to lose at that point or you wouldn't need to do it.

 

[ToddA1]

I finally got around to installing the A2 filter. I noticed the few air bubbles started becoming more air bubbles.

Very straight forward; I just needed to couple the return hoses together, once pulled off the "T". I used a brass fitting from my retired propane rig.

The A2 filter is slightly shorter and wider, but it still fit fine. No more bubbles.

-Todd

 

[TonyJetta]

Thanks, Todd!

I finally got to work on the Passat today, after dealing with a broken water main yesterday.

As I was pulling the boost control hoses, I noticed the clear blue line to the wastegate actuator was not filled with oil. However, the pressure feed from the turbo to the N75. The inside of this hose was coated with oil. I also noticed the blue line coming from N75 was coated for the 1st 12inches. I cut this section out. I was able to pry a little of this coating out, and it was not liquid, but a thick goo. Akin to rubber cement. So, I suspect the valve was failing.

I replaced the N75 and cleaned out the atmospheric hose with brake cleaner.

After a 40 mile drive, I've had no boost issues. However, the issue seems to materialize in the morning, when temps are near 70F, not 90F.

Tony

 

[TonyJetta]

Well, this mornings' Italian Tune-ups indicate that the low power / surging / limp mode seems to be fixed. No issues on a 70F morning.

I'll know more, as time marches on.

Tony

 

[50harleyrider]

Well, this mornings' Italian Tune-ups indicate that the low power / surging / limp mode seems to be fixed. No issues on a 70F morning.

I'll know more, as time marches on.

Tony

Amazing what a new N75 can do although I'm sure it's no better than a chemically "cleaned" used one according to the "experts" on here.

 

[ToddA1]

Anyone care to look and post their N75 vacuum routing? I'm trying to verify mine.

-Todd

 

[TonyJetta]

Anyone care to look and post their N75 vacuum routing? I'm trying to verify mine.

Here's a good thread. Scroll down to post #15. This is what I used to verify my routing last weekend.

Update:
The last 2 mornings have been ~65F. No surge, flat spot, low power, nor limp mode!

Tony

 

[ToddA1]

The link that you tried to provide is dead, but I appreciate the effort. I did more searching and eventually verified that my N75 is plumbed properly.

Glad to hear that you solved your issue.

-Todd

 

[reddtekk]

Surging woes

I came across this thread in my search to see if anything else than the diabolical N75 causes this surging issue in a B4 TDI. I replaced mine about a year ago and already have issues again. My valve still clicks loudly and boost is being regulated below (10-13 psi) what it settles at when the car runs normally (around 14-15 psi). Here is my list of things to try:

1. Try out Doorman's "lifetime warranty" on the nearly new valve.

2. Move N75 closer to the turbo to reduce volume of hoses. Why? The Jetta has the valve on the passenger's side and my dad hasn't had any trouble with it, but I've been through three. The issue seems like a control oscillation. Feedback says that the action taken to reduce the boost pressure wasn't enough, so the action (increased duty cycle of the valve) is increased. Maybe there's more delay in the wastegate reaction to pressure change because of the mile of tubing that they use on the B4. Marginal is good enough when everything is right, but the minute things are out of whack even a little bit we have issues.

3. Install oil mist filter in the pressure line from the turbo scroll. No doubt that engine oil makes it past the CCV on my somewhat tired engine. Arguably, a rering/rebearing would likely take care of most of my issues, but I'm not in a financial position to do that right now.

4. Mount the valve upside down. I autopsied my original valve. Like others have said, these are very sensitive to goo. The issue is that the valve is mounted in such a fashion that all of the goo settles around the moving parts. Inverting the valve so that the atmospheric vent faces down may help to discharge any goo that gets past the CCV and filtration rather than having it settle on the armature of the valve.

5. Go VNT. The VNT control uses vacuum - not regurgitated engine gook - to actuate the boost controlling mechanism. Again, like my tired rings, I've got no money to install the shiny hand polished low-mileage ALH VNT and manifold that I've got sitting on my shelf o' parts. I would need to flash my computer, fab stuff, and it would be ideal if that could be done along with the aforementioned ring and bearing job. Dreams are what we live for, right?

Hopefully I'll remember to post results as I try these items out. Happy compression igniting to all.

 

[ToddA1]

Years ago, I had an issue with the RPMs occasionally maxing out around 3800 RPM. This was right after a tune and nozzles. No codes were being thrown.


After verifying everything several times, I noticed my N75 was mounted upside down. Flipped it right side up and the car pulled all the way to redline. Never had an issue, since.

-Todd