twh

I remember reading someplace that the car has different valve settings while it is warming up. I did some quick Google and found this. I remember reading more descriptive things before than I found here. Seems like something isn't happening right during warm-up or something that only matter during warm-up isn't working.

"While the engine is warming up, VANOS improves the fuel/air mixture and helps to quickly warm up the catalytic converter to its normal operating temperature. When the engine is idling, the system keeps idle speeds smooth and consistent thanks to the reduction of exhaust gas re-circulation to a minimum. Under part load, exhaust gas re-circulation is increased to a much higher level, allowing the engine to run on a wider opening angle of the throttle butterfly in the interest of greater fuel economy. Under full load, the system switches back to a low re-circulation volume providing the cylinders with as much oxygen as possible."

mikegreen

Once you let it go 2 minutes and it gets smooth - if you shut off and immediately crank it again - does it idle OK? or does it need another few minutes to stabilize again?

Regarding the VANOS post by twh - do you have the ability to run the VANOS diag from a laptop? That'll exercise the motor and see if its hanging, I believe. Then again, that should throw an error anyways.

tonyb635

After it warms up a bit, the 1-2 minutes and I drive it. I can shut it down for quite a while and everything remains fine. It only seems to happen when it sits somewhere and becomes cold or what you would consider cold meaning what ever the OAT is and the engine does not feel warm/hot. I had an old 528e back 20+ years ago and it would take a long time to start after the car sat for about an hour. Otherwise it started fine. It turned out to be the check valve for the fuel pump allowing the pressure to bleed down. When it was cold, the cold start valve actuated and it started. Outside of those parameters the CS wasn't needed and so there was no fuel there. This is almost the opposite since it happens when I would consider the CS should actuate. Of maybe a leaky injector that is building up and the stumbling is from too much fuel. OK, I'm just rambling here....

mikegreen

I'm traveling now, but when I get home on Thursday night I can look in the service manual and see if it has any steps to troubleshoot this...

Do you have ncs-expert to run diagnostics?

tonyb635

Yes I have this but have never used it.

Duperstar

I have the exact same problem to the letter. My plugs were changed 1000 miles ago. I do have to swap my low pressure fuel sensor. I am hoping that helps. Otherwise i am checking the valves for cleaning. 2009 535i

tonyb635

Update to the situation. Again, when it sits over night or all day at work the problem is there. What I noticed today was, I arrived at work at 715 and had to go out for at 1030 for a little. There was no stumbling at all at start up or idle. I arrive back at work at 1145 and left again at 415 car was perfect! Ok, my question now, is there a way to check for a leaky fuel injector. Just a thought, as it seems now there has to be a certain amount of time that the car sits. Today, both times the car was cold for sure but only 3-4 hours instead of eight or 10.

Bonziat

I too have the same problem, but mine started when my job moved closer to home, so I don't get on the highway anymore. I recently poured a bottle of chevron complete fuel cleaner in my tank and the problem was gone for about two weeks then returned.

suckafree

Check your vacuum lines or replace them.

tonyb635

I'll grab a bottle of injector cleaner today and give that a try.