P0234 overboost still after new n75

So the story is this, I got a malone stage 1 on my tdi jetta alh. I went to pass three cars going 55 mph so i pinned it in 5th gear and once I hit 75 i went into limp mode or safe mode. I put in a boost gauge and when im pinned im boosting at over 30 PSI. I went through and checked MAF, Turbo actuator, all vacuum and found my N75 didn't hold vacuum. I put the new one in thinking that would fix it.

It did not fix it, exact same thing. High boost going into safe at 75 MPH.

Is the problem in the tune programming? Am I missing something? I'd really like to get this fixed before i leave for college in about a week as its quite a drive for me.

Any info please post for me. Thanks guys.

Could be a hole in the vacuum tubes, could could be a bad actuator, might even be the little black/white valve. Heck, might even be the turbo. Or something else I haven't thought of. Find a good diagnostic procedure for limp mode.
VW TDI Search Engine

BobnOH said:

Could be a hole in the vacuum tubes, could could be a bad actuator, might even be the little black/white valve. Heck, might even be the turbo. Or something else I haven't thought of. Find a good diagnostic procedure for limp mode.
VW TDI Search Engine

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I’ve checked all that, it’s not.


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Hussman said:

I’ve checked all that, it’s not.

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Hmmmm. When you tested your actuator:

- at what vacuum level did it start moving?
- at what vacuum level did it stop moving?
- did it transition back and forth smoothly?

did you recheck if you would hold vacuum? I'd change all the vacuum lines

ToxicDoc said:

did you recheck if you would hold vacuum? I'd change all the vacuum lines

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I didn’t recheck, the tester is at work, I just installed the new one at my house. But that must be the next step.


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Anyone else?

You said you've "checked all that".. what were the readings you got when you tested the actuator motion?

Vince Waldon said:

You said you've "checked all that".. what were the readings you got when you tested the actuator motion?

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All normal numbers with smooth back and forth


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Best to be specific on that stuff, even a half turn on an actuator can make a decent difference. Replied via email but for anyone else here's a few example logs, they are all from different cars.

How a stock car should roughly run: Note over-compensation by the N75 due to the spike, smoothing that out would make the car a hair quicker.
http://log.malonetuning.com/chart/231071

This is probably more like what you're seeing, erratic boost that the ECU and N75 cannot control. Looks like the owner improved it a bit where it clips to the third log, likely with an actuator adjustment.
http://log.malonetuning.com/chart/231026

Here is roughly what it should look like with a tune, there is a boost spike at lower RPM, but overall the boost is doing what the ecu asks of it.
http://log.malonetuning.com/chart/230608

Without data logging boost behavior or keeping close tabs on a boost gauge it's hard to make adjustments. VCDS will pay for itself in the long run by accurately pinpointing sensors rather than spending time replacing parts the car might not need.

Yay! Maybe I'm starting to understand this stuff a wee bit... Boost Actual vs Requested was gonna be my next suggestion. Whew!

Owain@malonetuning said:

How a stock car should roughly run: Note over-compensation by the N75 due to the spike, smoothing that out would make the car a hair quicker.
http://log.malonetuning.com/chart/231071

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The data is indicating about 30 pounds boost for a stock (factory) tune?
I thought the stock turbo is rated for 15 pounds if I recall correctly.

The last time I logged the boost I do not recall request going that high (under 20 iIrc) but actual was getting a bit over 25 pounds.

I thought my over limp mode was because the actual boost was higher then the requested by more then 5 pounds for to long of a period. 5 seconds maybe?

Those values are all including atmospheric pressure.

Owain@malonetuning said:

Those values are all including atmospheric pressure.

Click to expand...

That makes sense then.
I'm to use to my mechanical boost gauge.
Thank You