Hard start (long crank) on 4.8is

[FourPointEight-is]

I am having some trouble with my X5 starting. Sometimes it’ll crank and crank and crank for over 5 seconds. Then eventually it’ll start up. It’s never failed me yet. Also it seems very sporadic. Sometimes it happens and sometimes it doesn’t. It also runs fine when passing etc (no misfires under full load). Does it both when hot and cold.

Once it does start it splitters and coughs for about 10-15 seconds almost like it’s gonna stall out and the eventually settles in.

I scanned the DME, found fault codes stored for cylinders 4,5,7,8 misfire. Cleared them, went for a drive and came back but found no stored codes.

I viewed the live data for the engine RPM signal when cranking and found that it does give data even during the long crank. It spun up to about 150rpm until it finally “caught”.

The fuel in there is new, I just topped it up last week.

Any ideas?

I’ve heard it can be the fuel filter or the crank position sensor. I don’t just want to throw parts at it without verifying what the fault is though...