Dear Sir I found a problem in my E28 520i. When the water temp is warm(maybe 90*C),R.P.M.is800. In neutral gear. If I add the fuel make R.P.M.up,after I let the gas pedal off, the R.P.M. will go down to 500 then it will up to 800. I`m afraid of my car going to stop engine. I try to turn on my C.O. cap almost 5 circle,the problem will be better then before. I think it is not a good way to solve my problem. Do you have any idea? thanks!