Who has fought & solved unstable idle issues? (M54 3.0)

[80stech]

There is a ton of stuff that can cause this but often overlooked is a missfire due to a weak coil or poor spark plug. A compression test would probably be a good idea. Worn valve guides could be another issue.

[nick325xit 5spd]

Originally Posted by 80stech

There is a ton of stuff that can cause this but often overlooked is a missfire due to a weak coil or poor spark plug. A compression test would probably be a good idea. Worn valve guides could be another issue.

This is a good point. Misfires can be read as too rich, causing the car to lean out until it causes more misfires in other cylinders.

Injectors are a potential cause there too. A LEAN misfire looks like a RICH condition to the O2 sensor.