Will try and keep this initial post to the short version.  Car doesn’t feel as spritely as it should be so hooked up the bluetooth and torque.  No fault codes showing in the ECU.  Went for a drive and it seems to be boosting at about 5.5psi.  If you floor it in first it will spike up to around 15psi but long pulls in 2^nd,3^rd, 4^th etc all see maybe 8psi on the initial WOT but will then drop down to mid 5’s.  Spent last night and today reading various VW forums and also the first 15 pages of this forum when searching for ‘boost issues’ but none of the problems seem to be the same as this.

Understand it could be possibly vac pipe leaks which I am going to try and rule out tomorrow and going to try a couple of runs with the maf disconnected tonight.   There are no boost pipe leaks.  The N249, N75 or MAP are also areas to look at but not sure how to start ruling them out without replacing.

Hoping someone has come across this or got an idea where to start.

Below are a couple of screenshots showing various sensors on a longer 1st, 2nd and ^3rd gear pull on the dual carriageway.  The MAF looks to be reading a little low but not sure.

1st

^2nd

^3rd

 

1^st ,2^nd and 3^rd last night  1st was nearly 15psi

Edited 17 February, 20179 yr by SheffieldVRS

Have you uploaded the log file to the torque website? If so, you can download it from there as a csv file, import it to excel and do your own graphs, as well as see the "raw" data numerically. Not sure if you have an issue or not really, as one thing I have noticed with the boost gauge on torque, is that it starts with a value of -12psi - had the dash running on mine on the way to work this morning, and only ever saw 8psi - no other running issues either, so may just be the way it is calibrated?

48 minutes ago, octyal said:

Not sure if you have an issue or not really,

 

I drove quite a few of these when they were new cars and this one feels like its lacking.  When it comes on boost it pulls strong momentarily then you can hear the boost drop off and feel the performance reduce. 

 

I’m using realtime graphs add on for Torque and if you scroll through the graphs you can see all the numerical data at any given point.  The screenshots are taken at points of interest. Like the third pic is at nearly 4k revs but only showing 6psi.  Airflow meter also looks low at sub 100 given 4k should be full boost.  Threads like the one below have figures quoted higher for almost standard 150ps 20VT's  http://uk-mkivs.net/topic/54049-what-peak-maf-gs-readings-do-you-get/page-2

The boost seems right as vacuum showing at approx -20 at idle. 

Edited 17 February, 20179 yr by SheffieldVRS

Ran home with the MAF unplugged and it seemed to run smoother. No big hit of boost in 1st, all gears beyond that pulled smoothly. Couldn't feel any difference in power (compared to maf plugged in) pulling through the rev range. Turbo also sounded like it was boosting constant. Not sure if it means my MAF is knacked or the problem is elsewhere and being masked by then MAF being disconnected.

 

I'd be checking the fuelling if there's no codes 

 

Whats the mileage on the car ??

97k with full history

From experience if there's no codes it could well be that your fuel is having trouble keeping up with demand, really need those logs in csv format and ideally a requested and actual boost reading.

 

Got anyone near you that can swap pumps with ?? A mk4 golf gti would do as it's the same pump 

Quick update on this incase anyone finds it on Google with a similar problem.  Bought some electrical contact cleaner fom Halfords, cleaned the MAF and air intake temp sensor.  The MAF didnt really leave any deposits in the run off but the AIT had some baked on oil.  Quick rub of the AIT with a cotton bud brought it up looking nice.  Filled up with some premium petrol, turned the LPG system off and went for a drive.  Car now boosts stong hitting 10psi although will drop off to 8psi.  MAF values go up to about 160g at high RPM so it looks to have resolved.  Idle is also now smooth.

 

Well worth a £3.50 punt before changing the MAF.