engine? knocking

[trumpetr]

Need a bit of advice or suggestions on this.

My 95 525ia, has started a barely noticible knocking sound, under mild acceleration, and is only heard between about 2000, to 2500 rpm. It is hard to hear with the windows rolled up, however, with the windows down and paying attention to the sound, it is noticable. It is occuring at cold engine, and at normal operating temp, and does not get worse under a heavier acceration, like a normal knock would. On say, 3/4 throttle, it doesnt happen, either before or after the tranny kicks down. It only seems to be present between 2000 and 2500 rpm.
The thing is, i cant isolate the sound to the engine. Ive been driving around with my head stuck out the window, under a variety of speeds, throttle, and gears. Sometimes, it sounds if the sound is coming from under the midships of the car.
There are no other problems- the car idles smooth, accelerates smooth, no hesitation, no hard starts, and no CEL coming on.

This has started about 3/4 of the way thru a fill up of chevron premium, and i have since refilled the tank with premium from a Shell station- same deal, same noise.
The only engine mod, is an EAT chip, about 3 months ago, and there was no knocking after the install, and id say there is 3000 miles gone, since the chip.

Any thoughts would be appreciated.

Thanks-

[Derek A.]

Are you sure you are not hearing the Vanos system rattle or the intake resonating ?

M50's can make some weird noises.

[trumpetr]

Are you sure you are not hearing the Vanos system rattle or the intake resonating ?

M50's can make some weird noises.
Thanks for the reply, Derek.

Well, the sound it is making, is not what i would call a rattle, its more if a high pitched "tickety ticktickedy tick",,sort of noise, very much like an engine knock,,,except it doesnt do it when you would think a knock would present itself most, and its more subtle.
I wondered,,,,oil pump noise? If its VANOS related,could oil viscosity make valve noise worse? Im running 10-30 right now, in a mild climate- and the 'knocking' is the same, cold engine as warm.
Again, it just recently started this, and is present as said before.
I dunno,,,its a head scratcher.

I looked the intake over, and its very intact,,,air filter is clean, everything in place and no leaks.

I just dont want to overlook something that might grow into a $$$ problem

[Ross]

I've found it helpful to pull the car close to a wall to try and isolate noises. Usually a knock is a knock and you'll know it. I've never heard anyone descibe a bearing knock as a tickety tickety,whatever comfort that may provide.

[joshua43214]

I suggest taking it arround to someone with an experienced ear.

A bad wrist pin will make sort of a "tock" or deep "tick" sound when the engine is cold and will go away when warm. Its more metalic sounding than a rod knock, but deeper than valve tick. BMW's don't have much in the way or wrist pin problems so it is probably something else, but it is worth investigating. Can you make the sound "float"? This would be an indication of a mechanical engine problem normaly.

They had alot more vanos problems, so I would be inclined to start there.

[Ausmpower]

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