2011 R55 base (non-S) with 186K. Getting sporadic P303 codes for #3 misfire, Switched all plugs and coils from 1.2.3.4 to 4.3.2.1 to try to see if the problem moved.... no such luck. Dealership did a leakdown about 25K miles indicating possible leak on #3 intake valve. Light randomly pops on startup, but not consistent, and never while driving. Tried Seafoam to the tank and spray through throttle body but hasn't resolved these sporadic occurrences (maybe 1/5 starts). Does not affect performance, no stumbles on acceleration and no adverse affect on mileage. Not looking to spend $2K+ for head work to resolve a sporadic light. Ideas?

 

At 186K miles, the engine is probably worn. If you don't want to spend $2K+ on the engine work, then it might be a good time to trade in, get rid or just use the car until the engine gives up.

 

186k miles? That's one hard driven car..

 

Are you trying to squeeze another 14,000 miles out of her?