Quote:
Originally Posted by bavarianride
Interesting points. Is there any recommended intervals(e.g. every 100 miles) to run the engine hard from BMW?
Also is the buildup mainly at the back of the valve, hence does not affect the spray of air+fuel mixture?
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I don't think there is any recommendations from Bmw, but I don't think they intended their car du be driven between 1000 and 2000rpm all the time.
In the manual for my 1990 850i they put in that you from time to time needed to do a minimum 10 minute run above 3000rpm, mostly to clean the catalytic converter I guess. This car runs at 1900rpm at 60mph so you are rarely above 3000rpm in my country.
Yes the buildup is at the back of the valves, but also in the cylinder head, and the injectors sit in the middle. On older engines, like my 850i they sit in the intake runners just before the valve.
What I am saying is, if you have a very Eco friendly driving style, do a lot of short trips, sit stuck in traffic, never uses the upper half of the rev band, this may be why your car is not running right after a while.
I like to do full throttle runs when driving onto a new road, when getting on the motorways, and just chucking it around some twisty country roads.
I have never had issues with my cars not running properly until I got my 5 who obviously has had a previous owner who lived in a big city and drove it very nice.