Weird engine deceleration noise.
 

I've search and knows general BMW fairly well but can't figure out this noise. May be not using the right term?

Seems as this noise speed lags the engine deceleration noise. Sounds like it came from the Valvetronic? Car is 08 X5 3.0. TIA.
https://youtu.be/4uejj4LF9fo

I think this sound started today after I pickup from dealer for pcv heater recall. I don't remember hearing this sound when driving to dealer 2 days ago but I don't drive this car much as it is my wife's.

Sounds like it's coming from under #3-4 intake manifold. Not DISA valve, nor valvetronic solonoid.

Side note: the rattle noise at idle under the air filter housing is loud and hard, which wasn't there before. Not sure if the tech forgot some thing that cause this rattle and the weird engine deceleration noise when car is not moving (P or N). The same sound also present during test drive so it's not the driveline.

Anything else under there that could cause that grinding sound after the engine decelerate? TIA.

Hey Peter, long time no see! Hope all is well with you! Video is really hard to tell what the noise is at all or if I'm even hearing what you are hearing. Can you describe a bit more exactly what you are hearing/feeling?

If you think the shop didn't tighten down or left something behind under the airbox, pull it and find out for sure.

Let us know what you come up with.

Do you still have your E38 and E24? As you can see in my sig pic, still got the E38, but more of a garage queen now.

Yeah, still have my SC E38 but sold the Euro 635 and bought a 928 S4. Been busy enjoying life off grid with my Land Cruiser.

The noise is the slower decelerating whining noise that come after the engine deceleration noise. I removed the air filter housing and can't pin point it but its probaly not from the engine but definitely under #3-4 intake manifold.

Don't know if the dealer tech forgot to plug in the DISA valve after PCV recall service which may cause air to reverberate on deceleration.

The pcv heater valve, DISA, MAF is the only thing in that area so not sure what else it could be. Thanks.

Glad to see you're enjoying life. Wish I knew you were selling that E24 it sure was a beauty and I would have loved to have bought it from you!

I think you're probably right in your assumption, sounds a bit like something isn't hooked up properly. Are you getting any codes or anything?

No codes so may be the DISA valve might be connected ,otherwise it'll throw a code.

I am trying to find the new owner to see if he want to sell it back.

I had a feeling you'd miss it too much!

Update. It was defective pulley clutch on the rebuilt alternator that made the noise after the engine deceleration noise.

New alternator fixed the noise.

Great, glad you found the issue.