My m5 sat for about 2 weeks as I was away. There were significant storms while I was gone, so there was a lot of moisture around the car.
I started it up and had no issues beyond a slightly hunting idle (seems to be a regular occurance now), but the car hesitated bigtime, ultimately stalling. I limped it back into the driveway where it stalled each time I tried to start it. I had some pending engine too rich and misfire codes, which I cleared.
I pulled and cleaned the MAFs (pretty dirty), and replaced the plugs (definitely needed it). The car starts, idles roughly for 1-2 seconds, then stalls. I can keep it running roughly if I ease on the gas, but it stalls right after I let up.
My first thought was one of the CPS. Car is under extended warranty, so it will be going in to the dealer tomorrow, but I'm curious if anyone has any other ideas. I'm guessing it isn't the fuel pump/relays as it will continue running if I give it gas. I unplugged the MAFs and it seemed to run a bit longer, but still stalled.
Also of interest was my last trip to the dealer, as the car started slightly overheating. I assumed thermostat, but they supposedly replaced the fan clutch, and told me one of my cats is clogged. The temp gauge went to 2/3 3 miles down the road after picking it up. I took it back and they told me it was because of the clogged cat, and that they would replace it for $2800. I laughed my way home, and have some high-flow aftermarket units on the way. I hadn't driven the car since then. Could it all be related? On a side note, is the big nut on the crank fan an integral part of the fan clutch? Mine is quite rusty, which is curious if it's all one unit and mine was just replaced.
Any insight would be appreciated, as I'm not sure I trust what the dealer is telling me.
Not sure how much help I can be, but with all that rain, I am thinking water in the fuel/problem with fuel pump??
Also, there is an old discussion about water getting into the brake reservoir (under the drivers side air filter) and water getting into the motor (I think). It was from a member in NY and/or Long Island as I recall. You might want to look at that to see if water is getting in.
I wouldn't bother even trying to start it if it is under warranty, let the dealer sort it out.