Strange issue, coolant and misfiring.

About 2 weeks ago, my low coolant light came on. I was close to my parents house, so I took it straight there and parked it in the garage. I didn't have a lot of time to mess with it but from what I could tell, the coolant is leaking from around the bottom of the overflow tank/reservoir. When I parked it, it was running fine. The temp gauge never moved from it's normal operating temp. No signs of anything abnormal other than the fact that I had lost a little coolant from what I believed to be a cracked coolant reservoir, which I hear is very common. Well the other day I go back to look more closely at the problem. About 3 weeks have passed since I initially parked it. I still have not torn into it to confirm that it's a cracked reservoir (though I'm 90 percent sure), but when I went to start it, it would barely stay running and sounded like it was running on only 3 or 4 cylinders. There was a CEL on but I haven't had a chance to scan it. Does anyone have any idea what the problem could be? Is there anything that would indicate the 2 issues (cracked reservoir and terrible misfiring) are related, or would it just be pure coincidence ? It definitely is missing on more than one cylinder, so it's not likely that multiple coil packs went bad at the same time. I'm planning on going out there tomorrow to tear into it, just wanted to see if anyone could point me in the right direction. The car is an 01 330ci with 117k and has been meticulously maintained, though the cooling system has never been overhauled. From my brief research, I believe there is a coolant sensor located near the bottom of the coolant reservoir and that's a common place for leaks to occur on these cars. I'm wondering if it's possible that that sensor is my issue and is causing the car to run extremely rough. That doesn't make sense to me but I'm really just looking for any info that could help me. Thanks in advance!!





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