Rough idle E53 3.0i

[Johnoc70]

Hi. I have a rough idle problem. When the car is in drive but stationary the car idles fine. As soon as I put it in to neutral the revs drop down to about 550 rpm and after about 2 minutes I get engine warning light come on with lean codes on bank 1 & 2.
Thanks John.

[d_a_n1979]

Check the air intake boot from air filter box to throttle body & see if there are any cracks/splits... Sounds like it’s drawing in air after the MAF.

These boots are known for splitting, very easy to replace too & fairly cheap

[naturalaspiration]

Also this is a common issue:

https://youtu.be/V5H3m4AHKK8

The rubber cap perishes and air gets sucked into the manifold. I just stuck a rubber hose onto the attachment and plugged the other ende with a tight fitting plastic plug. Now as smooth as ever.

[Johnoc70]

I have replace the lower boot as it did have a small crack in the idle control valve connection hose. That hasn’t really improved it. Think I might need to get a smoke test done. I have noticed I now have an oil leak. Hoping fixing the leak may be the issue with vacuum leak

[Johnoc70]

Wondering if it may be the idle control valve. May replace it and see if that works