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Discussion Starter · #1 ·
Hi all,


First post so a couple of pics first :D






Issue I have is right as the turbo is spooling, boost increases and decreases as it spools up at peak torque. Once spooled and it's got to about 2500rpm IIRC it'll then pull through fine. But I'm probably loosing some bhp from the turbo not spooling up as well as it should.

I've tried a few different things to resolve, low mileage turbo, turbo vacuum controller, vacuum pipes, usual service type stuff so full service, cleaned EGR, inlet decoke, cleaned MAF.
I've also had the car pressure tested for leaks, so this tested the hot and cold side, I had a leaking exhaust manifold, this has been changed along with the gaskets so should now be fine. Inlet side was fine, so inlet/intercooler/pipes etc etc are all fine.

The car is now on about 126k, been mapped and decatted since about 105k and had this issue from probably around 110k. It's not getting worse or better by itself.

If the engine is cold, it obviously doesn't give as much fuel etc to be safe, and it doesn't then do it, once it gets warmer and comes to temperature giving me more power, it becomes more obvious. It almost feels like to me that I'm hitting a boost limiter at the lower rpm and it's cutting boost, then it's happy and letting it build again, then repeating the process over and over a couple of times until it's spooled up completely.


Any ideas on what it could be? I'm happy to try suggestions as I'm perfectly competent to do the work myself.

Appreciate any help!
 

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Discussion Starter · #4 ·
Any other suggestions? I found one forum post for a similar issue while searching, but no real ideas or fix for it.
 

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Discussion Starter · #6 ·
Nothing of use, just glow plug controller and a couple of glow plugs.

Nothing else. The fuel request vs fuel pressure achieved pretty much matches in by what I remember looking at the live data. Should I still check the pump out? Is there a FPR under the car as well as on the HP pump? Maybe worth a clean?

I haven't looked into the fueling side too much as the requested fuel is achieved, but the requested boost isn't quite until turbo is spooled up at the later RPM's where I can't feel the issue anymore
 

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Discussion Starter · #8 ·
I think they would have been, as it was fine when it was mapped (CNL Remapping Ltd) we went for a drive to ensure all was ok, and it was for a couple of months after that too.

Clutch started slipping a couple of months later, so I changed this along with flywheel and it seems to have been a few month later after that the issue developed. I don't think it's linked as it was OK once I'd done it for a while.
 

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Discussion Starter · #9 ·
If I got myself a gauge onto the vacuum line which controls the turbo, and read this while the issue was happening, I take it this would allow me to see if it's the turbo being told to fluctuate (e.g. limiter on map etc), or if it's boosting as much as it can, but then something else is causing the drops?
 

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Discussion Starter · #10 ·
My mate's lent me a boost/vacuum gauge so if weather holds out I'll get this plumed in over weekend and see if it helps narrow things down at all. :thumbsup
 

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Discussion Starter · #11 ·
Here's a quick pic of the boost fluctuation on live data, to help explain the issue.

Electronics Text Technology Line Font



Electronics Text Technology Gadget Electronic device


Any ideas appreciated.
 

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Could be a case of an uncoded maf sensor.
When you floor the throttle,does the boost start to come in and then is suddenly cut and this repeats itself twice until about 2800rpm,after 2800rpm the car will pull away fine?
 

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You will need DISV44 and 15 minutes of spare time.
If you accelerate gently you don't notice the boost cutting on and off?
This boost cut is a split second thing,yes?
 

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Have a read of the first sticky in the e46 technical section and see if it applys to you.
The 136bhp e46 320d and the 204bhp 330d suffered this issue and needed a new/replacement maf to be coded to the dde.
 

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Discussion Starter · #16 ·
Yeah that's right, you can't feel it with gentle acceleration.

DIS sounds a nightmare to install, and I'm not sure how confident I'd want to be programming ECU in case I messed it up. Anyone in South Wales confident with it I could pay to do so ? Can BMW do it? Or anyone who's not too far away, I don't mind driving a few hours to see someone competent at it.

It's not had a replacement MAF but sounds like reprogramming would be worth a shot
 
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