I own a 2008 550i, ~ 145000 mi. No huge, big ticket maintenance items up to now, but requires a bit more expense to keep it a solid car. Don't use it as a daily driver, but want it to be reliable enough for 750-1000 mi drives whenever I want to go on them. No history of major breakdowns on drives of this distance two to three times a year (although there have been some minor annoyances that didn't affect drivability).

Two days ago, I took the car out for a short drive. 5 mins from home, the check engine light came on and the engine began running roughly. I thought maybe I had a vacuum leak or something similar. Drove the car home and used another vehicle.

Today, I started the car up, wondering if it might be safe to drive the car to a mechanic rather than towing it. Lo and behold, the check engine light was off and the idle was normal. I drove the car about 20 minutes to do some errands, and the car seems to be functioning normally.

Any ideas why this would happen? Should I still be wary that there is a problem? TIA.

 

SO many possibilities. You really need to scan the car to see if it was trying to tell you something important with the CEL. Of course, a BMW-specific scanner would be the best bet, and it's almost a necessity if you plan on keeping your E60 for any length of time (better diagnostics = lower cost of parts and less labor, be it yours or the shop's).

OTOH, my personal philosophy is that a single occurrence of a problem does not constitute a trend, so I will tend to ignore it. These are complicated vehicles with LOTS of finicky electronics and mechanical bits that are nearly all capable of throwing a temporary fit, which is why the BMW-specific scanner can be so valuable (to closely track the issues your car DOES have, if only occasionally - that often allows for much more intelligent troubleshooting and lower-cost repairs).

 

Have you replaced the IVM (Integrated Supply Module)? it can be the root of many problems.
My car was miss firing, rough idling until I changed the IVM.

 

I would do as @habbyguy stated because the possibilities can be endless

 

+1 scan the DTC codes.