BMW v8s had an issue where injectors were mismatched- enough to let a cylinder here or there run very rich- car would run fine, but the engines would grenade when oil was diluted with the gas from these rich cylinders.


I bring this up NOT about your issue, but rather as an observation that 'it doesnt smell' or 'it doesnt smoke' or "runs great" is not a reason to ignore (or not be very concerned) about codes or CELs. Bad things can be happening.


Just an FYI.


Can you run a vanos functional test on the code reader you have? Slaggy VANOS solenoids/actuators can result in AFR issues, which can be very sneaky- it isnt a set thing, but at some parts of the RPM band, you are running rich. So it doesnt always happen the same. The fix is popping out the vanos solenoids, flushing them hard with carb cleaners and actuating the, with the proper voltage, then reinstall w new orings. Solenoids get fouled when people dont change the oil o time. A BMW specialty.



One final thing- but I am guessing you saw this- since BMW motors all share the same functions/componentry, dont focus only on "X5 w V8"... lots of other BMWs share these issues.


How many prior owners? All of them baby it, spend a ton of $$ and over-maintain it? Could have been a deadbeat owner in there. Also, BMW dealers can suck- the "BMW Maintenance" is notoriously poor- oil change intervals that are WAY longer than is healthy. Dont think because it was serviced at a dealer this buys you something. Its good that the serious repairs were at a dealer and may have a warranty on this work