[JonOhh]

The noise is especially prominent today, it's hot after being cold for a few days. After a four hour drive, I could hear it clearly on multiple occasions, typically when rolling off the throttle.

I know we discussed this, but it really does sound like knock/detonation. It doesn't have the consistency I would expect from a mechanical sound.

I will try to get a video of it up soon, I think it will help all of us understand what noises we are referring to.

[PhaseP]

Originally Posted by JonOhh

The noise is especially prominent today, it's hot after being cold for a few days. After a four hour drive, I could hear it clearly on multiple occasions, typically when rolling off the throttle.

I know we discussed this, but it really does sound like knock/detonation. It doesn't have the consistency I would expect from a mechanical sound.

I will try to get a video of it up soon, I think it will help all of us understand what noises we are referring to.

One thing that comes to my mind as something to check is the alternator pulley. It is an overrunning type pulley, it allows alternator to spin faster than the engine during deceleration of engine rpm. I don't know if it could cause the noise you are describing but not difficult to test it. You need to remove the accessory belt and see if the alternator pulley locks up and rotates with the alternator shaft in the engine rotation direction and in the other direction turns freely and smoothly if you block the alternator rotor. And if you block the alternator rotor, pulley shouldn't rotate at engine rotation direction. You can block the alternator rotor by sticking a screw driver through the holes, but obviously not into the wirings or anything that can be damaged. I had blocked the fan blades that are attached to the rotor from what I remember when I had tested for this years back once.

http://www.daycoproducts.com/what-ar...w-do-they-fail

[CDirks]

Subbed. There is a lot of really interesting discussion in this thread.

[JonOhh]

Originally Posted by PhaseP

One thing that comes to my mind as something to check is the alternator pulley. It is an overrunning type pulley, it allows alternator to spin faster than the engine during deceleration of engine rpm. I don't know if it could cause the noise you are describing but not difficult to test it. You need to remove the accessory belt and see if the alternator pulley locks up and rotates with the alternator shaft in the engine rotation direction and in the other direction turns freely and smoothly if you block the alternator rotor. And if you block the alternator rotor, pulley shouldn't rotate at engine rotation direction. You can block the alternator rotor by sticking a screw driver through the holes, but obviously not into the wirings or anything that can be damaged. I had blocked the fan blades that are attached to the rotor from what I remember when I had tested for this years back once.

http://www.daycoproducts.com/what-ar...w-do-they-fail

I checked the overrun clutch when I had the belt off for the 100k service -mind you, at the time I didn't know exactly what it is supposed to feel like, but it had a solid engagement in one direction, and after a bit of force, it would freewheel in the other.

I should add, it would take a bit of force to get it to initially unlock, but from then on it would be smooth. If I rev the shit out of it I get that signature buzz from the alternator as it spins down from astronomic RPM, and just the other day I noticed the shifter vibrating while the engine was idling but the alternator was still spinning down. Also, my engine seems to vibrate quite a lot, especially above 3000 RPM. New idler, tensioner, belt.

I wonder if the alternator bearings are shot...

[bbnks2]

Originally Posted by PhaseP

In E9X, none of the other N52's have this actuator valve, regardless of year or model. So they all have the same oil pump, silver or black engine cover, with the above exceptions.

pretty crackpot theory anyway.

N55 has the oil pressure control and you can tune it for whatever pressure you want at idle but you're not going to achieve it. You'll just get the same exact idle oil pressure and a cel saying oil pressure too low. Idle oil pressure is what it is (~38psi). I know this from first hand experience playing with the oil pressure set points.

There is a very small range where N55 reduces oil pressure in low rpm low load scenarios compared to a non map controlled car. High load like what is being described is NOT affected. You can review the charts in the N55 engine PDF. The region is very small, specific scenarios, and the reduction is very little.

IF there truly was some "lag" in vanos actuation because of -10psi oil pressure through a 1000rpm region than you would be getting codes for it. See the "cam bearing ledge" issue and how weeping some oil pressure out the cam seals causes codes. So theory doesn't really make sense.

Originally Posted by JonOhh

I could hear it clearly on multiple occasions, typically when rolling off the throttle.

Yeah I don't see how that would be knock/pinging at all then... Maybe look for a loose heat shield.

I doubt you're hearing "pinging." knock regulation is controlled so tight on these cars they pull timing before any audible pinging manifests itself. This isn't 1960.

Log the car. Run better gas or some octane booster. Check plugs/coils as maybe what you're hearing/feeling is misfires.

[JonOhh]

Welp, unfortunately having to revive this thread. I was never able to get a good recording, and gave up trying to solve the issue which got a little better and became livable.

Unfortunately since installing a Euro intake (with my original maf), the throttle control seemingly got much worse. A couple of weeks later, while driving around my windows down, I was able to hear exactly what happens when the engine hesitates and then begins responding: I can hear an audible spark knock sound. While I do agree with the above that this should not happen on a modern ecu like our MSV70s, I have spent plenty of times tuning engines and observing knock, and it sounds the exact same.

The main thing is that power output suddenly changes whenever the noise happens, and if it happens enough times in close succession, the engine power output is noticably reduced for quite a while. I have tried many different stations and have never put anything other than 93 in. Oddly, the engine sometimes makes more torque immediately following the noise which to me indicates an issue with vvt (vvt can actually throttle an engine to a slight extent by changing cylinder fill), but the long term power reduction to me sure seems potentially knock related. I am not sure.

As a next step I will be taking the new coils out of my other 330i, and the maf as well to see if there is a change in behavior. I am currently at 113500mi, and will soon be doing VCG and ESS. I do question how the VANOS solenoids are doing despite it always seemingly being on target in INPA.

[Robin427]

Hi,
i have the same issue plus i know two other N52 with the same as well.
one with 150t miles two with ~90t miles, all from '05-'06,
searching the reason for some time but unfortunately without succes.

i think it is the vanos or oil presure relation as well, maybe for a reason at low rpm the oil presure is not sufficient to perform a large camshaft shift.

you can hear this only while driving with open windows and close to walls or other car, correct ?

Originally Posted by JonOhh

If I remember right, my 06 330i, since I've gotten it, has sometimes made a slight single "clink" noise at heavy throttle low rpm. Originally assumed it was the exhaust flapper... flapping... but I've unplugged the solenoid and it's still there.

Most of the time, my n52 doesn't rattle or clunk under acceleration at all- it's actually remarkably smooth and quiet, but occasionally there's this sound we're currently talking about, and I really want to know what it is.

I remember reading a long time ago that there was once a flash to help alleviate the lifter issues, which put the oil pump in a higher output state at lower rpm/idle. I will keep trying to find the thread, but the owner reported that it resolved his lifter tick issues. My logic is, if it is the VANOS not getting the oil pressure it needs, this would also alleviate that as well, and hopefully silence it.

On top of that, I'm willing to sacrifice some efficiency for the peace of mind that oil pressure, even during low rpm operation, is more than sufficient to keep all of the engine propperly lubricated.

As said before, I'll keep trying to find it, but for now I have no concrete validation that this update exists.

Jon

[JonOhh]

Originally Posted by Robin427

Hi,
i have the same issue plus i know two other N52 with the same as well.
one with 150t miles two with ~90t miles, all from '05-'06,
searching the reason for some time but unfortunately without succes.

i think it is the vanos or oil presure relation as well, maybe for a reason at low rpm the oil presure is not sufficient to perform a large camshaft shift.

you can hear this only while driving with open windows and close to walls or other car, correct ?

That is correct, I usually hear it with the windows down while driving past things.


Also- just to clear this up: the N52 DOES have a variable displacement oil pump, but it is entirely passive in that the output pressure regulates the flow. When output (oil pressure) falls below a designed value, the pump geometry changes and provides a higher displacement.

Some N54s and all N55s have an actual solenoid to bypass the oil galley back to the crankcase.

[F31B48]

Originally Posted by JonOhh

That is correct, I usually hear it with the windows down while driving past things.


Also- just to clear this up: the N52 DOES have a variable displacement oil pump, but it is entirely passive in that the output pressure regulates the flow. When output (oil pressure) falls below a designed value, the pump geometry changes and provides a higher displacement.

Some N54s and all N55s have an actual solenoid to bypass the oil galley back to the crankcase.

I have the same detonation issues. It gets bad in summer when it's hot outside. I have changed my fuel from 95 octane to 100 and that has eliminated it mostly, so it is definitely detonation. I can still hear it slightly with the window down. The engine perfoms a lot better on 100 as well.

Apparently the fuel quality we have here is considered poor, so i have put it down to that. The car runs perfectly other than this issue.