Boost cutting out and coming back

[truCido]

I've had a search around and I can't really see what this relates to....

Only recently when at about 4000 - 5000 revs, boost will drop completely for a sec or two and then come back...

I'm guessing its something like the N75? or a pipe caving in? not really sure, can anyone give me any pointers?

 

[mrk]

mine does this too and it sounds like n75

 

[Beaker™]

I had a similar problem once, turned out to be a coilpack. Not quite sure why or how, but replaced all four and the problem vanished.

 

[truCido]

oh thats strange, not sure why a coilpack would make the car behave like that. I think I'll find a N75 valve and have a go

 

[Beaker™]

I know, i think it was producing a weak spark under load and casuing the car to hesitate. It would rev up to about 4k then boost would drop for a second then suddenly cut back in and boost as normal.

 

[truCido]

yeah exactly what I've got. We're you able to get vag-com on it? and see if it was showing anything?

I've got a spare coilpack, but I guess I'd have to try it in each and go for a run.

Just phoned SEAT and they want £55 for a N75....maybe I'll find someone on here selling lol!

 

[Beaker™]

IIRC vagcom didnt show the fault. Worth trying your spare though as you've got one to hand. Also, could you borrow an N75 from anyone with a Golf/Audi/Seat etc?

 

[truCido]

Very true...might rip my mates cupra apart

 

[pj1985]

Mine does the same and does not show a fault on vagcom. Problem is it doesnt always do it so I might have to wait a while to find out which coilpack it is if I chang them one at a time starting with one.

For an N75 they are about £40 from vagparts but Alex at TTS might be able to do you a good price aswell.

 

[Smoki333]

I think its something to do with the N75.

Have any of u bypassed it?

Since i've bypassed mine, i have never had the problem.
I could be driving on boost, hit a bump (example) then i'd jolt along with the accelerator pedal if u get me and i'd see i have no boost on the gauge then suddenly get all boost again.

 

[truCido]

You dont bypass the N75 thats the N249, but yes I have bypassed it

 

[Smoki333]

sry i meant the N249, that seem to sort it for me

I could tell when i'd get the boost an when it would cut out then count an it would come back.

 

[truCido]

definately not that I did the bypass ages ago, although I have recently replaced the N249 with a new one as the old one melted lol

 

[pj1985]

Bypassed mine a while ago and it did it before and still does it now. Only does it at 4k revs so if definately something to do with the load at that rpm which is why its more likely to be a coilpack.

 

[truCido]

well 4500 rpm is probably your peak power....

 

[Beaker™]

Try your spare coilpack, sounds very much like a weak spark thats being blown out under load.

 

[truCido]

I was thinking it could be the sparks...maybe the gaps to big? I replaced them not to long ago with IK22's