[Lightningfastbmw]

2011 BMW 535i with 91k miles.

On cold starts my car starts up completely normal. But when the engine is warmed up and I start the car there is a very loud and high pitched noise. It idles rough with the rpm going up and down around 1000 rpm. Feels like the car is reving itself. Trouble code that I have found is the P0171 code which means that the fuel system is to lean. Also there are several cylinders misfiring when I plug into the OBD.

Though, when I rev the engine up to about 3000 rpm the sound goes away and it idles smoothly. Before this issue came up I had added one 12oz bottle of Techron Complete Fuel System Cleaner to the gas tank. Not sure if this has to do with anything, just putting it out there. 2 days after adding the Techron I started to hear this loud and high pitched sound coming from the engine bay. I took a look at the engine air filter and it looks clean and like new.

Here is the link to the video on the sound.

View post on imgur.com

Any advice or info would be greatly appreciated. Thank you!!

[Surly73]

Video link isn't working. What happens when you pull the oil filler cap off when the sound is happening?

If it stops and there's a lot of suction your CCV has failed. It's integrated into the valve cover. The noise is air being sucked past your front or rear main seals and they will end up damaged by this so a fix should happen soon to limit collateral damage.

Here's a Youtube sample video to get you going:
https://www.youtube.com/watch?v=DIMpIAkWeNI

[Lightningfastbmw]

Originally Posted by Surly73

Video link isn't working. What happens when you pull the oil filler cap off when the sound is happening?

If it stops and there's a lot of suction your CCV has failed. It's integrated into the valve cover. The noise is air being sucked past your front or rear main seals and they will end up damaged by this so a fix should happen soon to limit collateral damage.

Here's a Youtube sample video to get you going:

Just warmed the engine up and got it to make the sound. I took the oil filler cap off and the sound stopped immediately. There was a bit of suction to it as well to take off the cap. Will do more research and possibly change the CCV valve. Really appreciate your advice!

Here's the link again. Hope it works. Seems to work on the mobile device app but not desktop. https://m.imgur.com/gallery/6SsS1ss

[Surly73]

Originally Posted by Lightningfastbmw

Just warmed the engine up and got it to make the sound. I took the oil filler cap off and the sound stopped immediately. There was a bit of suction to it as well to take off the cap. Will do more research and possibly change the CCV valve. Really appreciate your advice!

Here's the link again. Hope it works. Seems to work on the mobile device app but not desktop. https://m.imgur.com/gallery/6SsS1ss

Sure seems like CCV. I would replace promptly to limit damage to other components and systems.