E46 318TI N42 rough idle on cold starts - where to start??

[NutStrikesAgain 3]

Hi everyone,

Got this issue with my car - been doing it since I got it about 18 months ago.

The idle is really rough and keeps dropping until the engine warms up. Once the engine is up to temperature it is completely smooth - see the video that I recorded on my phone a while back below.

I used to get random occurences of bad idle even when the engine was warm but this stopped after I replaced the PCV oil seperator and breather hose.

Replaced since I've owned the car: sparkplugs, rocket cover gasket, eccentric shalt sensor gasket, VANOS o-rings, PCV, intake manifold gaskets, vaccum pump gasket.

Where should I start to try and work out what's wrong? Throttle body was clean last time I checked it

 

 

[B.M.W Ltd 951]

It needs to be diagnosed correctly with the right type of scan/diagnostic tool

[zero 1162]

What Glenn said

[NutStrikesAgain 3]

Any recommendations on places to go in Auckland (not North or West)? Other than BM Workshop or BMW themselves

[B.M.W Ltd 951]

What area do you live ?

 

[NutStrikesAgain 3]

1 hour ago, B.M.W Ltd said:

What area do you live ?

 

Manukau 

[B.M.W Ltd 951]

I've sent you a PM

[NutStrikesAgain 3]

Okay so BMW's verdict/diagnostic is that the issue is most likely a vaccum pump or brake booster leak that is causing the idle to fluctuate. Found that the brake pedal was quite hard to press.