Whats the definition or "rough idle" 540i\6sp

[Tiger]

Did you noticed how fast our RPM accelerate? That's why... BMW designed these engine as semi-racing engine... which is why our torque is at higher RPM... Then they decided not to do this on the 4.4L where their gobs of torque is available at much lower RPM.

[Tiger]

Yep, if you had a failing Nik.. the door would shake tremendously up and down when opened... Otherwise, normal enigine would shake just a tad.

[wmann]

Not concerned about engine failure, unless the BMW dealership totally botched up the leakdown and compression test. The door movement is not visable with the door open at idle, but if I put my hand on the door I can feel some movement as I would expect.

I was more interested for the fuel consumpsion aspect, I don't expect the world, but if I could get 20 mpg instead of the 17 I get now I would be very pleased.

What does everyone esle get for MPG??

Thanks for all the input! Bill Mann

[632 Regal]

my 530 tops out at 22 mpg.

[digitaldragon03]

Did you noticed how fast our RPM accelerate? That's why... BMW designed these engine as semi-racing engine... which is why our torque is at higher RPM... Then they decided not to do this on the 4.4L where their gobs of torque is available at much lower RPM.

The car does seem to accelerate better at higher engine speeds. I wonder why BMW decided to do this.

Anyways, now im worried, my door does shake noticably when its open and i havent warmed up the car. I would say it does move up and down around half an inch. The only reason I havent thought much of it is because it only happens in mornings. Once its warmed up, the idle is pretty smooth. I always thought that the nikasil rough idle would continue even if the car had already been warmed up.

[winfred]

that sounds like a intake gasket leak, ether one of the port gaskets or the throttle body, it usually kicks up some 02 sensor/lambda codes after a while. while i have the intake off i do all of the gaskets and the pcv plate

The only reason I havent thought much of it is because it only happens in mornings. Once its warmed up, the idle is pretty smooth. I always thought that the nikasil rough idle would continue even if the car had already been warmed up.

[SharkmanBMW]

if it only runs rough when it is cold it could be the rear part of the intake manifold, pcv plate.
I think that is the name, mine was rough at start up and would smooth out after a few minutes, I changed that part and it went away - sweet!