Still having boost issues (post turbo swap)

Grave Robber · Jul 30, 2017

prior post here: http://forums.tdiclub.com/showthread.php?t=477720

tl;dr: sudden loss of power getting on the freeway, diagnosed as probable turbo failure. got home and had tons of oil in the intercooler piping. replaced turbo and all vacuum lines, the main shaft had tons of end play and there was oil all over the outside casing of the turbo. Issue persisted. replaced EGR valve, still no fix.

On to the present!

I am still getting the p1556 error code and having jumpy acceleration even after replacing the most likely culprits. I even went ahead and replaced the N75 valve with no change (the one on the driver side). I can bypass the N75 valve altogether (and I think most of the vacuum components) and it runs just fine, a bit down on power, but without the jerky acceleration. After I kill the engine I can pull the vacuum line off the reservoir bulb and I can hear the hiss of vacuum being released, so I don't think the pump is at fault.

I have a vacuum pump available but I'm not sure how to check all the lines for leaks (which is another possibility)

What do you guys think?

Also, could it be the other N75-esque valve near the middle of the firewall (under the windshield wiper cowling)?

edit: please be as descriptive as possible, this is my first turbo diesel and Volkswagen. Put it into Mustang terms if possible (we are a simple bunch)

williambill · Jul 30, 2017

Just a thought since you said you replace the vacuum lines. Check to make sure the lines didn't get reversed on the N75. Make sure the "vacuum" port goes to vacuum source and the "out" port goes to the turbo actuator only. I once helped a fellow TDI'er with similar problems and turned out that's all it was. Simple to check and costs $0.00.

Also, if it was a new turbo you replaced to old one with, the linkage on the actuator has to be set properly, IIRC. Somebody please correct me if I'm wrong, but I believe it needs to be set using a vacuum pump to start moving at 3-5" hg and hit the stop at 18" hg.

Grave Robber · Jul 30, 2017

that's the first i've heard of calibrating the turbo actuator on the mk4.
I followed this guide: http://www.myturbodiesel.com/wiki/turbo-removal-turbo-replacement-on-alh-engine-bew-engine-similar/

Which port is the vacuum and which one is the out? aren't they different size hoses?

wonneber · Jul 31, 2017

Grave Robber said:
that's the first i've heard of calibrating the turbo actuator on the mk4.
I followed this guide: http://www.myturbodiesel.com/wiki/turbo-removal-turbo-replacement-on-alh-engine-bew-engine-similar/

Which port is the vacuum and which one is the out? aren't they different size hoses?

I replaced my actuator and had to fine tune it.
I was getting over boost, had to lengthen the actuator rod.
Have you checked if the actuator arm is moving when you start the car?
It should.
I get vacuum to the actuator at idle (not full vacuum), it drops off when I start driving.
If no vacuum start tracing the vacuum lines backward one step at a time.
If the N75 is hooked up wrong it could cause this, as well as the one way valve in the vacuum line being backwards (no vacuum).
Also, search for the limp mode thread, it should be in the stickys.
I has a post with the vacuum hose diagram.
Print the image.

williambill · Jul 31, 2017

Which port is the vacuum and which one is the out? aren't they different size hoses?[/QUOTE said:
They may be different size hoses, I can't remember off hand. On an OEM N75 it has vacuum and out physically molded into the body corresponding to the appropriate port. Google images for "VW N75" and you'll see what you're looking for.

Also, I'm assuming you have an ALH? The how to link you posted is for a later model engine.

Grave Robber · Jul 31, 2017

The thread links to how the BEW differs, but the whole article is ALH specific

How would I hook up the vacuum pump to check for pressure? I'm completely new to vacuum issues

Grave Robber · Jul 31, 2017

I was under the car when my brother started it and the actuator arm for the turbo moved a d responded to throttle input, is that good?

Also, got an ultragauge hooked up to it and psi is sitting at -0.58 with an occasional -0.73. Could there be a faulty boost sensor (if it has one)?

BobnOH · Jul 31, 2017

The actuator is operating normal. You want to connect a vacuum pump with gauge onto the actuator. It should start to open at 3.5 to 5 "/hg. If not, adjust the length of the rod with the double nut.
I can't comment on the psi value, I've not used that method for diagnostic.

Grave Robber · Jul 31, 2017

Okay... After cleaning the contacts of the maf wiring with contact cleaner I'm getting p0102 but the gauges still shows between 12 g/s (idle) and 90 g/s (at 4500 rpm) for maf readings and no other codes.
I'm so confused, any fuses I should be checking?

BobnOH · Jul 31, 2017

P0102 could be the car was started with maf unplugged or it's not plugged up tight or it may go away on it's own, you can clear it.
Yes there are fuses involved with management system, can't tell you the numbers off the top of my head.

Grave Robber · Jul 31, 2017

P0102 went away after driving for a bit, but it turns out my brother didn't have a vacuum pump with gauges, he just has a vacuum pump so I'm pretty much dead in the water until I get one.
Thus car is beating me down, I've had 4 days of wrenching on it and it's sat for almost 2 months...
Any idea on how to test the vacuum system without gauges?

UhOh · Jul 31, 2017

Go rent one from a local auto store.

wonneber · Jul 31, 2017

If you had a vacuum gauge you could tee it in the line to the pump.
You would need 2 tee's (another to tee into the line going to the line you are checking.
Also I bought 10 feet of vacuum hose to run my vacuum pump into the car.
Plain rubber, not the cloth covered.
Harbor Freight has an inexpensive one.

Rrusse11 · Aug 1, 2017

For $22 at Harbor Freight there "brake bleeder" did the job for me.
I was having a lot of lag with the turbo. Turns out the actuator rod
wasn't hitting the stop until it hit 25"hg. Now set at 19"hg and voila!
Lag problem solved.

BobnOH · Aug 1, 2017

Vacuum gauge with pump is pretty standard diagnostic equipment, get one. Not expensive

Nevada_TDI · Aug 1, 2017

I once upon a time had a genuine Mity-Vac that grew legs and ran away; I now use the $22.00 Harbor Freight one. I had one die and HF replaced it w/o problem; it wasn't new either.

eddieleephd · Aug 2, 2017

Adjust log and adjust some more.
People talk about when it's supposed to open, however, I had to adjust the overboost out so it was only 150 over in vcds.

Start with vacuum pump and then log and adjust it to driving requirements.

snakeye · Aug 2, 2017

wonneber said:
If you had a vacuum gauge you could tee it in the line to the pump.
You would need 2 tee's (another to tee into the line going to the line you are checking.
Also I bought 10 feet of vacuum hose to run my vacuum pump into the car.
Plain rubber, not the cloth covered.
Harbor Freight has an inexpensive one.

Great advice. Is connect it directly to the actuator's vacuum line first, though, to monitor whether the N75 is conscientious pulling the right amount of vacuum. If the vacuum level bounces around or drops suddenly you might have a leak or perhaps a faulty N75 valve.

Speaking of leaks, I'd inspect the big vacuum hose, where it attached to the pump. It's known to loosen and leak, especially while driving, when the car vibrates more.

BobnOH · Aug 2, 2017

eddieleephd said:
..............People talk about when it's supposed to open, however, I had to adjust the overboost out ...................

That's cause it's in the instructions. Some will tell you open at x, fully open at y, but you can only make 1 adjust.
Nothing wrong with a bit of tweaking to improve performance.
Once you have the thing adjusted, proceed with troubleshoot rest of system, teed in vac fitting helps with that.

wonneber · Aug 3, 2017

BobnOH said:
That's cause it's in the instructions. Some will tell you open at x, fully open at y, but you can only make 1 adjust.
Nothing wrong with a bit of tweaking to improve performance.
Once you have the thing adjusted, proceed with troubleshoot rest of system, teed in vac fitting helps with that.

2x ^^^
Once you know the pump is pulling enough vacuum and wiggling the nipple does not loose all the vacuum then test it's getting to the actuator.
The base adjustment on my new actuator was OK even though the old and new actuators were slightly different.
I had to lengthen mine and log runs with a few more adjustments over time.
I've only had 1 over boost since (at lease a year) on a long hill with cruse control & AC on.

eddieleephd · Aug 3, 2017

wonneber said:
2x ^^^
Once you know the pump is pulling enough vacuum and wiggling the nipple does not loose all the vacuum then test it's getting to the actuator.
The base adjustment on my new actuator was OK even though the old and new actuators were slightly different.
I had to lengthen mine and log runs with a few more adjustments over time.
I've only had 1 over boost since (at lease a year) on a long hill with cruse control & AC on.

I would tend to think that you only had one overboost reported, or that caused limp mode.

I had over boost regularly, however, it was constantly over boosting.

The instructions essentially get you near proper adjustment and you need to fine tune it for driving.

I went by the tutorial and still had overboost issues.
5 logging and adjustments to get right where it needed to be.

wonneber · Aug 3, 2017

eddieleephd said:
I would tend to think that you only had one overboost reported, or that caused limp mode.

I might have chimed in a few other posts but mostly was reading here, trying, logging & such.
It was going on for a few years.
Once I put the boost gauge in I had it in control for the most part.
I finally started the rod adjustments and drove the car for a week or two for results.
I have access to a lift on weekends.

I have only had one on a long hill with cruise control on in a good while.
I was surprised it did not affect my fuel mileage.

I still want to stuff a bore scope down my exhaust pipe and a light from the other end to see if the particulate filter is clogged.
I use to get 50-53 MPG when the car was new, now 46 to 48 is the best I can do,

Grave Robber · Aug 7, 2017

OK guys, I tried out my new Pittsburgh vacuum gauge and I have made zero progress...

The system seems to be leak free (each area holds vacuum for a bit and ever so slowly goes down), replaced all the lines and tees and each section seems to hold vacuum just fine, and the system runs with fairly constant vacuum and I can even see the turbo getting vacuum under throttle. I also hooked it up to the actuator for the turbo and it starts moving at 3 inHg and has full extension at just over 19 inHg. I also put dielectric on the connector for the MAF (because someone had a similar problem and this was a fix).

The system is still showing P1556.

I replaced the MAF as part of my troubleshooting and I'm wondering if the new MAF could be the cause. The jerkiness of acceleration is gone with the MAF unplugged, still low on power though

The only thing that seems wrong with how the car drives is a lack of power and a jerky, lungey characteristic under constant throttle, almost as if I was constantly going over speed bumps.

the car's been sitting for almost 3 months with this same issue.

Replaced turbo, MAF, N75, EGR valve, vacuum lines and tees. I dont know what else it could be...

Nevada_TDI · Aug 7, 2017

Grave Robber, I have read through this thread more than twice and I am thinking I have another question for you: Is your car bone stock? This is important stuff how long have you had a boost gauge installed, was it before the problem started or was it after in a desperate measure to figure out what is happening?
So you are cruising down the highway at say 5/8 throttle and you see the boost come up like it should to say 12 PSI, and if you hold your foot at the same throttle input (stay with me here) does the boost fall from 12 PSI to 7 or 8 PSI and yet the engine continues to accelerate like you have just pushed on the throttle even harder, or does it just stay at the 12 PSI (just an example) until you let off of the throttle?
What I also want to ask is does the "jerky lungey characteristic" occur right around 3k RPM, or is it always at right around the same boost level? Please respond here or PM me.

Matt-98AHU · Aug 8, 2017

Seeing as how the code is underboost, if you can't hear an obvious boost leak or EGR leak/exhaust leak pre-turbo, my first suspicion is a vacuum leak.

Since you have a new turbo, I wouldn't worry about the adjustment on the actuator too much... Doesn't hurt to check, but you might just be chasing your tail there.

What I would do is take your new vacuum gauge, remove the small diameter hose that goes to the main vacuum pipe/check valve assembly between the vacuum pump and brake booster. That one small diameter hose is what feeds the rest of the small diameter vacuum lines. Go straight there and measure how much vacuum you have at idle.

25" mg is on average what a healthy system puts out. I frequently encounter cars that are at 15" mg or less because of a leak right there. Either the vacuum pipe to the brake booster is cracked or the nipple on the vacuum pump is loose and causing the leak. In my experience, those are by far the two most common causes of vacuum leaks and subsequent low boost pressure faults on ALHs.

wonneber · Aug 8, 2017

Did you try spraying the entire boost tubing path from the turbo, to the intake manifold with soapy water?
Include the fins on the intercooler and the intake to head area where possible.
Check for loose intake bolts?
My quick scan of the thread I did not see boost readings when you go down the road and accelerating.

Nevada_TDI · Aug 8, 2017

In my previous post I asked a lot of questions as I had been going through the same symptoms, and pulling my hair out using the same basic fixes. Mine finally started to tell me what was going on; I got a "timing deviation" code which did reset and I now have a QA error that will not reset and now my car will not start at all. I did order a re-sealed and tested pump from Frans, and i am waiting to install it when I get the tools and the needed friend at my car at the same time.

BobnOH · Aug 8, 2017

This is an outlier for sure but.... Mine once had that same code, only at top end acceleration. Didn't go away until I repaired a wire (#2or3) that goes direct from the IP to ECU. Makes no sense, but I had it for months. The little wire was hard to locate. It was in the bundle that goes under the battery from IP. Had a small nick that looked factory. Only took 2 years to find. Main symptom was slow down shudder from he!!.

Grave Robber · Aug 10, 2017

Nevada_TDI said:
Grave Robber, I have read through this thread more than twice and I am thinking I have another question for you: Is your car bone stock? This is important stuff how long have you had a boost gauge installed, was it before the problem started or was it after in a desperate measure to figure out what is happening?
So you are cruising down the highway at say 5/8 throttle and you see the boost come up like it should to say 12 PSI, and if you hold your foot at the same throttle input (stay with me here) does the boost fall from 12 PSI to 7 or 8 PSI and yet the engine continues to accelerate like you have just pushed on the throttle even harder, or does it just stay at the 12 PSI (just an example) until you let off of the throttle?
What I also want to ask is does the "jerky lungey characteristic" occur right around 3k RPM, or is it always at right around the same boost level? Please respond here or PM me.

The car is bone stock as far as I can tell, I bought the ultragauge (knock off scan Guage) to diagnose the boost issue.

It shows -. 58 or -. 73 for boost psi, regardless of the rpm or load on the engine. not sure if it's a car error or scanner error, or if it's just not producing boost. If I t off the vacuum line going to the turbo actuator into my vacuum gage I can see changes in vacuum (less vacuum with more throttle) as I give it throttle.

The jerkiness of the throttle is everything from idle on up (and it goes away with the maf unplugged, but still no power)

Grave Robber · Aug 10, 2017

Matt-98AHU said:
Seeing as how the code is underboost, if you can't hear an obvious boost leak or EGR leak/exhaust leak pre-turbo, my first suspicion is a vacuum leak.
Since you have a new turbo, I wouldn't worry about the adjustment on the actuator too much... Doesn't hurt to check, but you might just be chasing your tail there.
What I would do is take your new vacuum gauge, remove the small diameter hose that goes to the main vacuum pipe/check valve assembly between the vacuum pump and brake booster. That one small diameter hose is what feeds the rest of the small diameter vacuum lines. Go straight there and measure how much vacuum you have at idle.
25" mg is on average what a healthy system puts out. I frequently encounter cars that are at 15" mg or less because of a leak right there. Either the vacuum pipe to the brake booster is cracked or the nipple on the vacuum pump is loose and causing the leak. In my experience, those are by far the two most common causes of vacuum leaks and subsequent low boost pressure faults on ALHs.

I remember checking the vacuum at idle with the vacuum gauge taking the place of the reservoir and it was around 22-24 inHg. I'll check at the pump next.

What would such a boost leak or egr leak sound like? The engine still sounds a bit different from what it sounded like before these issues.

Still having boost issues (post turbo swap)

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