I'm experiencing rough cold start ups for the first 30 seconds. After this period of time, problems disappears completely.

- It seems it's temperature related. I couldn't replicate at the dealer when the car was parked outside in the sun for 2 days.
- I can always replicate when the car is in my slightly colder garage
- In P or N, RPMs are not really steady. If I engage D right after I start the ignition, the car shutters, hesitates and feels like almost engine would shut off at times when driving away slowly from the lot or garage.

- Maybe unrelated, but when car is parked for a longer period of time, car would not move - after 3 days parked, I engaged D immediately after starting and the car would not move at all. It started moving after about 7 seconds and I even had to press the gas pedal.

I'm guessing it's transmission or fuel related. Dealer suggested using different fuel.

(The last mentioned "issue" might not relate to the rough start ups, as I've experienced it on my previous BMW (330d) as well and considered in normal. Something with the lubing, because oil in transmission settles down in the pan after longer periods of time.)

Any thoughts?

 

What you're describing is not normal operation. If you are still under warranty a more thorough diagnosis is needed. Of course you could always use the process of elimination ... starting with the easiest - use fuel from a different brand/station. Engine operation will definitely affect transmission engagement; Our cars have so many computer interactions that if operating conditions are not met the transmission might "think" it's time to go!!

Net net, I think your car is having an ignition/fuel problem - especially on cold start! Exactly what is causing it is anyone's guess BUT guessing can be very very expensive. As I said, a more thorough diagnosis is a MUST! Good,luck with getting it sorted out!

 

I think it started appearing when I bought new spark plugs (NGK Iridium).

Could maybe incorrect gap alignment on the plugs cause this behavior?

 

Could be a plug gap or perhaps a coil pack failing.

 

Well, the NGK Iridium IX should not be adjusted according to NGK. So I used .032" (0,8mm) factory gaps.

The gap on OEMs is supposedly .043" (1,1mm).

Could that 0,3mm smaller gap cause hiccups when cold?

 

I always thought with the correct part number, NGK should come pre-gap the the correct size.

 

Nope, it doesn't work that way.

For example, on N62TU (V8) engines, the same part number lists Bosch and NGK spark plugs (probably whichever are available at the dealer can be used). Bosch is platinum and has a .039" gap. NGK is laser iridium with a gap .043".

If you want performance/enthusiast spark plugs, then you can use NGK Iridium IX which use pure iridium. BMW doesn't list these at all as part numbers. They are pre-gapped at various gap sizes and according to NGK, shouldn't be altered. If a particular iridium spark plug model fits with with its dimensions, you're supposedly good to go without altering the gap.

So I kept it per NGK's recommendation. Could that be an issue?

 

SO, thanks for letting us know that you made a small change and coincidently your cold start problem started to happen! think you may have partially isolated the problem to something done during this DIY. ... I doubt that a couple of hundreths difference in the plug gap is causing the problem. It may be something as simple as an incorrectly seated coil pack ... or when removing the wires one of them was damaged. Are you sure the plugs were screwed in and torqued to the recommended tightness? Another situation I've seen is that in the process of getting a spark plug deem into the recesses of a motor that some gunk got on the tip and fouled it up - could that have happened to you?

 

I haven't tinkered with it at all. I just supplied and handed my own spark plugs to BMW authorized service and they installed it.

I believe they do this every day so it's a small chance that they could screw it up, but maybe I could start from there and have them re-check (or use OEM plugs if nothing wrong is found)?

 

I had a problem very similar to yours - BMW ended up replacing two injectors and new injector seals for all of them.