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  #1  
Old 05-29-2017, 09:49 AM
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2005 x5 3.0 diesel engine louder and loss of power

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

Last edited by Upex; 05-29-2017 at 01:39 PM. Reason: Typo correction
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  #2  
Old 05-29-2017, 10:02 AM
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You could give this a read to see if it covers anything you missed:

BMW Diesel Engine troubleshooter guide power problems and smoking issues.
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Old 05-29-2017, 01:04 PM
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Engine roar and not reving properly is typical of bad MAF. I would try cleaning it with MAF cleaner anyway.
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Old 05-29-2017, 01:37 PM
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Thanks both.

Zulu, will have a read, thanks.

Bcredliner, revs ok, just hasn't got the go behind it. Have tried cleaning maf, no difference. Also no difference if unplug maf. Would this indicate it's bad, as always believed it should get better with maf unplugged, if it's the maf at fault?

Thanks, Upex
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Old 05-30-2017, 08:37 AM
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Partially blocked cat? If the exhaust is blocked downstream of the turbo, then the back pressure might slow the turbo, reducing boost. Opening the EGR relieves the back pressure a little and boost levels return... Maybe...?
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Old 05-30-2017, 08:39 AM
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PS. How much oil on the compressor outlet seal is "too much"? A light coating after 200,000km or are you taking enough to be running and dripping?
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Old 05-30-2017, 02:23 PM
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Thanks wpoll,

There not much oil in pipes, considering the turbo been there for 12 years and 140k miles, hard to gague but just enough for 3 or 4 drops at bottom of turbo to cooler hose in 10 mins (ie waiting 10 mins, not after driving 10 mins lol), certainly not bad.

're blocked cat, would that allow high speeds, as she can still do above speed limits etc and holds speed steady on hills etc and revs easily to the red line, I'd have thought a partial blockage would get worse at higher rpm, but am guessing here and it is one of the possible causes on the link Zulu posted.

I do like the premise that the egr being forced open would help and thus the engine get quieter though, makes sense.

I've ordered a leak back tester, as perhaps if one injector not flowing, she running on 5 cylinders, so noise and low on grunt? Am I barking up the wrong tree here? Would a duff injector throw a code?

The stuck variable vanes sounds (from Zulu link) plausible to, but unsure how to check them and why the engine would be noisier if this would be the case.

Would a bad maf get bit better if unplugged, as mine doesn't lol.

Cheers all,

Last edited by Upex; 05-30-2017 at 03:22 PM.
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Old 05-30-2017, 03:12 PM
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Reread your post and think you are on to something with the EGR. You might want to do some research into EGR problems/cures.
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Old 05-30-2017, 03:35 PM
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Thanks Zulu, read a lot over past month or so.

The EGR closed holds petrol, so appears to be closing fine, and with it open with hand vac makes engine quieter (like it used to be) at idle.

I cannot find anywhere to confirm what vac it should get at idle, full throtal or anywhere inbetween, so can't confirm if controller working correctly or not (but it's a brand new bmw control unit, and have tried another new aftermarket one as well).

I would have presumed that both turbo and EGR vac controllers would operate the same and allow same vac levels (but they dont at idle anyway), however if egr supposed to be shut at idle (i think it should be), then it is, as vac level below opening pressure. But, turbo controller is supplying much higher vac at idle.

I don't know if applied vac at turbo closes or opens the waste gate, i presume no vac is open. But regardless, i cant understand how the 2 units allow different vac pressures at idle, when voltage and resistance are the same between both units.

Still looking for any specs on what they should be regards vac and voltage etc, but i cant find that needle in the www haystack.

Are you thinking of anything in particular?

Thanks, upex
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Old 05-30-2017, 05:56 PM
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Quote:
Originally Posted by Upex View Post
The stuck variable vanes sounds (from Zulu link) plausible to, but unsure how to check them and why the engine would be noisier if this would be the case.

Would a bad maf get bit better if unplugged, as mine doesn't lol.

Cheers all,
I think swapping out the turbo unit has eliminated the vanes as a possible issue but the control to the vacuum control to the vanes could still be an issue. As you say, it seems unlikely that a VVT issue would make the engine noisier.

Not sure about the MAF on our M57N engines - does traditional petrol engine wisdom transfer to these diesels? Heck, there isn't even a throttle body!

I guess if the MAF was returning totally mad values to the DDE, then unplugging it and forcing the DDE to fall back to lookup tables might make it better but it seems you have eliminated this anyway.
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