Author Topic: Boost Issues - Mk4 Golf ARL Hybrid Turbo  (Read 1882 times)

Offline colz1234

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Boost Issues - Mk4 Golf ARL Hybrid Turbo
« on: 15 August 2018, 12:08 »
Hi all. Have been having boost issues with my car for the last couple of years, have been in a few different garages, had it scanned with vagcom while being road tested and apparently was all good, have had boost hoses / vacuum hoses checked and a couple of dodgy looking vacuum hoses replaced, new maf and map sensor (well within time ive been having the problem), intercooler replaced.

As its a hybrid turbo full boost comes in about 2700rpm. What happens is you put your foot down at say 2200, it picks up a little and you can feel it building a bit (but not as much as it should be) then when it hits about 2600 it kind of backs off a bit then slowly accelerates on up, almost like the turbo isnt working, but it is because the boost gauge i think is reading about 20psi at this point.

If you keep pushing it through the gears after a few mins it will normally go into limp mode, where the turbo cuts out altogether (no boost at all registered on gauge) and the engine note changes a lot deeper and louder. If I turn the car off, and then back on again (yes I know a its dodgy while driving along) and put my foot down, it has full power (full boost) for about 5 - 10 seconds, then it trails off and it goes back to kind of half power.

One fault I have had come up with vagcom, this was about a year ago now mind, was 17965 - Charge Pressure Control: Positive Deviation, which was told most likely is turbo sticky vanes. Now i was beginning to believe that the turbo may be the problem, but  since i have full boost, and i have it everytime i start the car for the first 5-10 seconds, i don't think it can be the turbo as surely it would not do that?

The only thing I can think of is something electrical? As I have full boost until the ECU does its checks and then its like nope, your not having that. But why is it doing it?

I have also visually checked the wiring around the n75 valve and cant see anything wrong, no wires hanging out anywhere.
Any thoughts of what it can be would be muchly appreciated