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Had this happening for a while now, a case of "I'll get round to sorting it"
The car started to do this shortly after having it mapped (around a month or so)
The boost drops from around 20psi to 5-6psi and will stay like this until I switch the ignition off and back on. More often than not it will be fine for the rest of the day when it’s done it once but will happen again first drive the following day suggesting it’s happening when the car is cold. There is no splutter or sign of it happening other than one second its boosting fine then the next 5psi.
Going to get my dad's code reader on it next week to check it over but in the meantime any help/ideas are appreciated!

Who was it mapped by?

I assume youve checked all hoses under the bonnet?

seems odd that its happened since the remap, not sure how that can muck it up :/

also how are you checking the boost - is it a gauge that you've fitted, make sure that thats all correct because it could be another issue instead.

Harney wrote:Had this happening for a while now, a case of "I'll get round to sorting it"
The car started to do this shortly after having it mapped (around a month or so)
The boost drops from around 20psi to 5-6psi and will stay like this until I switch the ignition off and back on. More often than not it will be fine for the rest of the day when it’s done it once but will happen again first drive the following day suggesting it’s happening when the car is cold. There is no splutter or sign of it happening other than one second its boosting fine then the next 5psi.
Going to get my dad's code reader on it next week to check it over but in the meantime any help/ideas are appreciated!

Sounds like your car is going into soft limp mode. The car wont boost more than 5 psi in soft limp. I would check the map first, my guess - fueling, but many other factors cause soft limp. Scan for codes on vagcom.

Right, finally got round to scan the car after just putting up with the problem for far too long now.
The code I got was 17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
I have taken the forge 007p off and checked that the piston is not stuck, which it wasn't and checked for split hoses and can't see or hear any.
I did notice that the valve next to the d.v. (PCV valve i think) on the intake pipe was covered in a thick film of oily sludge so I cleaned that off to try and spot where the oil maybe coming from but couldnt tell if this was the problem or not. While I was there I took off the intake pipe and flushed it through with carb cleaner along with cleaning and re-setting the throttle body. All this has made the car pull a lot better and make slightly more boost but I am still getting the limp mode and fault code.
If I clear the fault code, it comes back on the moment the engine is started.
Any advice?
If no one has any ideas my next plan is to work my way through replacing the valves on the vac system such as n75, n249, n80 and try a new pcv valve.
Might get it sorted by the time im ready for selling it!!

I had a similar problem last year with my car and replaced the PCV valve as was covered in oily residue, told they get clogged up and stop working or the diaphram gets damaged and they dont perform as they should. Not saying it may cure your problem but seemed to cure mine. Cant remember the code my car threw up when it happened though.

Part number for PCV valve is 034 129 101B cost about £12 or so. Worth a shot, start cheep and work your way up is my moto lol.

Cheers for the part number pal! For £12 its worth a shot! Ill get one ordered for the weekend and post the results!

This sounds like over boosting.

Which would be to do with the map.

I would personally take the car back to whoever mapped it and see if there are aware of any faults with their maps that they have already rectified and if not have them check it.

9N3 Turbo wrote:This sounds like over boosting.

Which would be to do with the map.

I would personally take the car back to whoever mapped it and see if there are aware of any faults with their maps that they have already rectified and if not have them check it.

I agree, its soft limp. I doubt the PCV will cause that.

When my pcv was damaged, my car had a jerk, not soft limp.

I would run a log on vagcom and look at the map. Check your requested VS actuals.