Another limp mode

I've read and reread and read I'm at a loss.
2003 alh 3 inch turbo back no cat no muffler. EGR delete and asv delete. Intake cleaned. New turbo vanes actuator set to 18 inch with a mighty vac.
New n75 valve new vac lines. Turbo tested manually with a vac pump to verify vanes move. N75 is oe vw replacement. Unplugged maf 0 change.

17964 code and limp mode.
Vac pump is verified working. Vacuum ball not leaking
Snow screen is clear. All charge pipes are good and no leaks

Is there anything else someone could suggest me looking into and at?

Make sure the vacuums lines are routed correctly.

JB05 said:

Make sure the vacuums lines are routed correctly.

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Thank you for the reply, double checked route. Followed this

in VCDS as soon as i rev to 1450rpm Group 11 gives me an Error and stops reading. anything under 1400rpm it reads ok.

has anyone experienced this?

thnaks

I don't know about group 11 specifically, but I did have issues with limp mode and it seeme that just about everything that could go wrong, did go wrong that would send me into limp mode.

Ultimate, I needed a new VNT actuator, new MAF, new MAP sensor and a new N75 sensor.

I did get a P1556, Charge Pressure Control: Negative Deviation at they very end of my diagnostics and I believe that was for the bad N75 sensor. I had a P0108 for the bad MAP sensor.

If I remember, NONE of these came up as a CEL, I just had a generic Code Scanner hooked up and was reading for anything that I could to help me find my issues.

You can read my post here from years ago, maybe it will help!

http://forums.tdiclub.com/showthread.php?t=329445

Update

on my particular diesel, my vac pump is outputting 25-28'' of vacuum. from the check valve it goes into the N75 and the N75 is what actuates the VNT actuator or what some think is the wastegate.

my N75 at fully opened operation only outputs about 10'' of vacuum.

my actuator was adjusted to the 15-18'' as set forth by all the online guides.

after setting the actuator to around 10'' of vacuum as put out by the n75 i now have full power and no more limp mode. im not sure why my n75 is only outputting 10-12'' of vacuum. i have new silicone hoses, new n75, new check valve, no leaks etc etc... it may just be the pierburg n75?

the vanes move freely and are easy to move no sticking and have full range.

either way, if the turbo or something else is on its way out, the car drives great now. no MIL and no drop in economy/performance. i hope this helps someone. Match the actuator vacuum to the n75s output.

how do you do that? hook a vacuum gauge to the n75 line that supplies vacuum to the actuator and measure what the actual vacuum is everytime it cycles using VAG COM Channel 11 in the basic settings.

it will open and shut the n75 valve and you measure the vacuum each time it opens the n75.

hopefully this helps someone in a similar situation.

mk3j, it is odd that your N75 'at fully opened' only measures 10". It's just a valve
that is either open or closed to the vacuum at the inlet. It is unable to regulate
the vacuum other than by the PCM signal sent by the ECM. I would verify that the
actuator isn't leaking or that there isn't a lack of vacuum for some other reason.

mk3j said:

.........................New turbo vanes actuator set to 18 inch with a mighty vac.........................

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Just so it just begins to move at 3.5 to 5.0.

OP, have you tried swapping the N75 with the N18, to isolate the N75 valve as the possible reason why there is only 10" at the actuator?

Yes I swapped with the unused n18, bought a cheap amazon n75 and tried that. then a pierburg and then replaced the pierburg just cause I can with another one. All new btw.

Checked for leak down the valve and it doesnt leak pressure. for some reason is only outputting about 10" it's very strange. It holds too. Yes the actuator begins movement at about 3"

whats really strange is the pump 100% i know is putting out correct vac pressures. i replaced the white and black check valve, that should be the only thing between the pump and the n75 and it still only outputs 10''

im kind of done troubleshooting it at the moment as it seems to be okay with being so low on vacuum. its been weeks of going back and forth with this car and so now that im finally able to drive it out of limp mode i will do that for a spell.

i will update this thread if i come across anything else, its possible i will play with it again

You indicated "vac pump is outputting 25-28 of vacuum"

Have you checked it's getting to the top port of N75?

When you start the car the arm on the turbo should move. Check while the turbo is cold for safety.

Tee into the line going down to the actuator with a vacuum gauge.
With the car running you should get 10 inches of vacuum (roughly).
When you take off vacuum should drop off. (sounds backwards)
It this what you are saying in post #10?

started digging into this again since the weather is getting better. my vacuum pump is now very much under performing. i took it apart, replaced all the seals, it seems fairly worn out. 289k on the clock and its original so i think its ok to replace it at this stage.

only outputting 15in of vac now.

i will replace this pump and report back. i only paid attention to the total vacuum it produced not how quickly so with the new pump ill be comparing. the old pump was slowly able to produce 15in of vacuum. i hope my conquest is able to assist someone lol

mk3j said:

only outputting 15in of vac now.

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Disconnect the hose going to the brake booster & plug it. (at the pump end)
Check the vacuum once more.
There's a spot in the plastic line that's hard to see that may crack.

wonneber said:

Disconnect the hose going to the brake booster & plug it. (at the pump end)
Check the vacuum once more.
There's a spot in the plastic line that's hard to see that may crack.

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as it turned out my issues came primarily from the brake booster hose! no visual cracks or anything. i replaced all those and we are in business now! i hope this helps someone

mk3j said:

as it turned out my issues came primarily from the brake booster hose! no visual cracks or anything. i replaced all those and we are in business now! i hope this helps someone

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Glad you got it fixed & posted the solution for others.