So I've been working on my Mini R52, and I got it working pretty well - replaced the fans (engine and PS), Replaced all the relays. No more overheating, everything running fine for weeks.
Then last night, freezing temperatures hit, and now the car won't start. It turns over, runs for a second, then starts coughing, and dies. Trying to start it right away results in another cough, and nothing.
However, if I let it sit for a few minutes - it repeats. Will run for a second or so - then coughs and shakes, and that's it.

Checking the codes with Torque Pro only shows a P0500, which claims to be a speed sensor. This is new, but not sure if it's related, or just caused by the poor starting/running situation.

I'm starting to think "Fuel pump" or "Fuel filter". But I would have expected a code for that. Has anyone else seen anything similar? There is no water in the car, and the DME is not wet or corroded or anything.

 

>Battery voltage. Should be 12.6V cold iron. In this case very cold iron. Good possibility it's low. Recently had a similar issue - cranked fine, but some cough and stumble at start - in a sub-20F cold snap but the car recovered and ran normally. Low voltage on a battery approaching end of life (3 years in December). It doesn't take much juice to crank over these motors; running them normally / reliably requires a solid 12V+. They hate hate HATE low voltage.
>Once started should be in the high 13's / low 14's V idle voltage across the battery terminals with the alternator under load (e.g. headlights, radio, and heater blower on etc)
That sorted, some other possibilties
>Fuel tank level low / empty (no shame, we've all done it, even if few will admit to it )
>Listen for fuel pump to spool up then shut off after a couple seconds when you turn the key to "ON" but not crank. Check fuel pump fuse if you don't hear it.
>Could be ice in tank / lines / pump - would try starting again after ambient temp > freezing. Then add Heet® or other such water chaser + full tank of quality premium fuel.
>Can check fuel pressure at the rail; there's a Schrader valve (borrow a pressure gauge kit from O'Reilly's / Autozone etc) on the (U.S.) driver end of it (car's left). Nominally 55psi.
>Check spark while cranking - plug removed and grounded (Bzzzt! Watch your fingers!)

 

Thanks - this must have been it. Wouldn't start for two days, had a couple of hours with the sun out. And it just slowly started getting better, and now runs fine again. Put n a bottle of iso-heet just in case. I'm guessing my full tank of 93 octane with no alcohol is to blame. My choices are 89 with 10% or the 93 (no 91 nearby), so I'm going back to the 89.

 

Keep in mind that 10% is ethyl alcohol, as in booze. Not needed in the car to run it normally and put there for other reasons than to chase water. Iso-Heet (red bottle) is iso-propyl (rubbing) alcohol, the yellow jug is methyl ("wood") alcohol. And the original issue may or may not be water (ice) related. If we see you pick the thread up again in January we'll know that it's probably something else.

Did the battery static and charging voltage readings check out ok?

 

Yeah - Battery was fine, I replaced it last winter because it did the old "running rough when cold" thing. I'm pretty certain I just had a bout of bad gas at this point. I've not had any issues with gas like this in ages, it caught me by surprise.

 

Update: It happened again this last arctic freeze, but this time the big thaw didn't help out.
So, since I had a fuel pump and fuel filter already, I went ahead and replaced those on the off chance that something had happened to them. Removing the old fuel pump was a pain, and it was actually in two pieces as I lifted it out (the top and spring were separated). Unfortunately, replacing both of those didn't fix it either... I tried waiting for the fuel pump to prime, etc. And no dice.
So finally I pulled the plugs, and they seemed to be covered in fuel/soot. I think I fouled them when trying to start the car over the past week or something. Or maybe the fuel pump just took much longer than I thought as I replaced the plugs, and it started right up and kept running.
All of this with no codes. lol.