[StiffUpperLens]

Hi all, need some advice if you are willing.

I have an E90 330D N57 engine variant. I know the 330D isn't all that common here but the N57 is and I doubt my problem is specific to the single turbo version of this engine.

Over the past few weeks my car has been under powered, its maybe lost about 20% over all.

A year ago I cleaned my intake manifold, cleaned the swirl flaps and replaced the glow plug module while I was there, so I know all that area is ok and not clogged up.

Despite that, coinciding with loss of power, the car threw up errors relating to swirl flaps. Hoping it wasn't the actuator, I went to remove the intake again and check for build up over the weekend.

However before that I ran a few tests on ISTA to try to expand the picture a bit.

First I tested the turbo pressure actuator, the actuator rod moved perfectly with no restriction at all, but ISTA showed that while it was reaching its set point, there was no response from the turbo - actual pressure didn't change.

The strange thing is that when i run live data in the car when driving, I can monitor the boost set point against actual boost and they are the same, well, mostly the same.

If the actuator is moving fine, could the vanes in the turbo still be stuck? I would have thought that would be impossible? I haven't seen inside one to know who their coupled.

So then I did an Air Intake test (I can't recall the ISTA test name sorry), this tests the MAF sensor, Air Intake temp, outside pressure, manifold pressure etc.

The test takes pressure measurement with engine off, then engine on, idle, revs to 3700, then 2000rpm and finishes.

That test failed and when the engine was running at 3,700rpm, it bellowed white pungent smoke out the exhaust, smoke that really badly stung my eyes and stunk my house out the whole weekend, it still smells actually.

The engine also misfired/ran rough at those revs.

I followed up with another diagnostic, this time no faults in the Swirl flaps, instead the MAF has thrown a fault. Cleared many times and it is still there.

On cold start I get rough Idle, the car is now down on power about 50% but when warmish, it drives smoothly and idles fine.

Its not using any more fuel than usual. Oil level is stable, coolant is stable, no mixing of each either.

Yesterday I cold started it, it ran like a tractor. I unplugged the MAF and she idled perfectly, so clearly that's kaput.

So question:

On the testing, at 3700rpm it bellowed smoke. However driving it, there's no smoke. Foot the floor and still no smoke.

Could the MAF be causing this?

Or could it be the turbo? Its getting up to boost according toto CARLY live data, but fails the test in ISTA?

Oh, other tests I conducted were:

EGR valve actuator - passed (i pulled out to clean anyway)
EGR Cooling flap - passed

Would anyone be able to make any sense of this?