ok my friends 545 seems ot have a very very slight rough idle I changed the coil packs this weekend on it (the back ones were a right bastard) and its still there. Plugging it in brings up no error codes what so ever so we cant even start to trace anything. Have changed the coils as mentioned above and also done the plugs, something is obviously causing it to have a slight rough idle but everything must be within tolorace otherwise we would have been able to get a error code up. Do theses cars have a ICV valve? its starting to piss him off and I'd like to get to the bottom of it

 

Is the engine actually idling rough or is it just the rev counter that is "twitching"?
I had a "twitchy" rev counter a little while ago and it was a faulty rev counter causing the problem. No error codes but you could see it moving at idle. They changed the instrument panel under warranty and it fixed it.

 

remember it a v8 not a even firing 6. you will get a little roughness compared to a 6.

 

i thought the rough idle was a common problem with the 545 and supposedly the dealer has to reprogram the computer to fix that error, i had that problem before and it went away after i did the computer program upgrade hope that helps or if that's the same problem you have.

 

it has all the latest software from BMW so I dont think its that, my 545 doesnt have a rough idle this def has one you can feel it, all the other 545 we have been in do not seem tohave this slight niggling problem...