Engine stumble / cough on cold start up
Every morning my X5 starts like ****. At least.. 9 months of the year. Only during the warmest summer months does she not do this.
I turn the key long enough to fully turn the motor over (just like the manual encourages you to do). Yet, every time... the motor stumbles (barely fires) and then coughs (small back fire sound coming from the engine bay). No back fire at the tail pipes. "ruckka tuckka".. almost stalls.. "cough (then a small bang / ca-chunk sound)". Then rough idle for 5 seconds. Then all is fine.
My dealership's mechanic is really good. He almost never gets stumped on a problem. But, they say they cannot reproduce the problem. They've kept the car over night on two occassions. Nadda. No engine error codes either.
My driveway is on a slight down hill. Could this contribute to it? But I've parked her nose first (slight up hill then) and she still does it.
This can't possibly be good for my engine. She sounds terrible. I've resorted to giving it a little gas at start up. If I just baaaaaarely give it a tiny bit, she starts beautifully. The danger is though, that you give it too much. Then the engine starts with a .. VAROOOOM, which isn't good for the engine. Darned electronic throttle makes it really hard to get it just right. Teaching my wife how to do this... not really fair to her. Mechanic says NOT to start it this way. What choice do I have tho ! ?
Anybody else getting this?
Cam sensor? Some start up idle circuit set too low? Any insights appreciated. Thanks guys.
'02 Z3 Coupe 3.0i [Hellröt II - Walnuß]
'03 X5 3.0i [GrauGrün - Beige]
'01 Z3 Roadster 3.0i [AlpenWeiß - TraumRöt]