XSeries-forum

New turbo fitted but issues....Drives fine until kickdown then won't rev above 3000rpm, switch off & start up again and fine until i boost up, then won't go above 3000rpm again. Plugged in and showed 4521 code. Any ideas??

Did you fit new vacuum pipes.
If not then check them for splits.

Can't see any adrift or hear any air leaks

Not sure you would hear any at idle and your problem is at speed and kickdown, If not absolutely 100% sure then I would recommend renewing vacuum pipes otherwise you could end up chasing your tail and spending big money.

Is you x before or after sept 03?

it was built dec 2005. I've checked all the vacum pipes with a little pressure gauge and none is leaking. Also took off the little valve by the turbo and checked the little air filter etc, and vacum checked it. All good

[quote="henrym3"]
Not sure you would hear any at idle and your problem is at speed and kickdown, If not absolutely 100% sure then I would recommend renewing vacuum pipes otherwise you could end up chasing your tail and spending big money.
[/quote]

yes only at kick down or maximum boost, then goes into 'limp' but switching off and starting up again clears it, until nect time I put my foot down

Had the same problem with my 8 series years ago,  took it to an indie and they pulled up misfire fault codes, an old timer there said does the exhaust rattle in the morning when cold, I said yes ?????
It turned out to be a collapsed Catylitic converter.
Only did it when I kicked down at max boost, it would go into limp mode within seconds.
Drove perfectly any other time, reset with a simple off and on of the key.
If it can't get shut of the exhaust gasses fast enough it goes into limp mode.
Maybe not your problem, but has happened to someone else on here too.

I'm asking this question from an interest point of view, if you accelerate gently will it go past 3k revs