Hi all,

Apologies for the long post, but have been trying to resolve for about 2 months, and were struggling, so wonder if you all have any ideas as to possible issues and fixes for a loss of power and louder engine noise.

During a long drive, she got louder and didnt have the power she did pre issue. No warning lights presented and didnt hear anything pop etc.

Brought her home and put in garage, they said seal on cooler pipes or turbo were cause. Didnt say a thing about any error codes, just wanted £1000 to fix.

I got all seals from air entry to manifold and changed them all. Added a new turbo with new oil feed and return pipes. No change. So put into a different garage, he ran codes and gave me a long old list (50) ranging from glow plugs to bluetooth button being stuck. Main one being 4521 charge air pressure control.

I've since removed the new turbo and put old one back on, as the new one was catching in it's housing, too much bearing play.

I've also changed all vac hoses as far as engine mounts. I've replaced both vac controllers with new genuine bmw units. Cleaned egr and inlet manifold. Replaced map sensor (was a cheapo one which immediately threw an error, so put original bmw map back on which cleared the error) and replaced glow plugs and controller. Also changed air and diesel filters and changed oil.

Fuel pressure showing 300-330 bar at idle, going up to 1200+ bar when driving.

Charge are pressure circa 40 higher than ambient when idling, and goes up to approx 2400 when giving it some.

Very good starter, fires up 1st time, every time, within 1s. Idle is steady. Have unplugged maf and it made no tangible difference.

I've checked all the charge pipework and cooler best I can, no signs of leaks etc, and car is not throwing any codes now (bar unrelated, ie the webasto, phone etc - using pa soft and bmw scanner 1.4.0), but she is still down on power and louder under load.

I've tested the readings at vac controllers (the new bmw ones):

EGR side:

Vac pressure (measured between EGR and controller):
At idle 0.4 or 0.5 bar,
Slowly increase to 2k revs, 0.4 to 0.5 bar,
Fast increase to 2k revs, drops to zero.

Voltage and resistance:
Controller itself 16.4 ohm
At the plug:
Power off - 41.5 k ohm
Power on but engine off - 0 ohm and 9.2v
At idle - 0 ohm and 11.5v


Turbo side:

Vac pressure (measured between turbo and controller):
At idle 0.8 bar,
Slowly increase or fast increase to 2k revs, no change until drops to 0 upon release of throtal.

Voltage and resistance:
Controller itself 16.6 ohm
At the plug:
Power off - 1.25 m ohm
Power on but engine off - 0 ohm and 9.3v
At idle - 0 ohm and 11.5v

The one thing I noticed though, is that whilst the EGR side controller was off, I applied manual vac (via hand pump) to EGR whilst engine was idling, at .5 bar there was no difference, but between 0.6 and 0.8 bar of vac the engine got quieter, and sounded much more like it used to pre issues.

I assume that the egr opens at say 0.6 bar then, and with it opening, the flow of exhaust gas has somehow made it quieter - could this be a sign of where the issues are? When is the EGR supposed to be open and when closed?

Can't find any tech specs to confirm if any of the above is normal or out!

Acceleration is not half what it used to be, and engine is a lot louder, as if actually running at 3k more revs than indicated.

I still need to change turbo, as the old one is starting to have faint sound of sirens, and is showing oil in the compressor outlet, but given swapping it didn't change at all, I doubt the turbo is the root of all the power loss?

Anyone any suggestions, as I'm fresh out now. Doing my head in and already cost a bomb, likely on stuff not needed!

Cheers all