I have an 87 260e, of which I bought 14 years ago. Up until about 2 years ago, the car always had an idle speed of 10 on the RPM guage. However, ever since about 220,000 miles, I have noticed that the car idles at either 7 or 10. I would like it to stay at 10 all the time, and have tried changing the air filter, but this changes nothing. What does this mean when the idle is running at 7 instead of 10? Does something need to be replaced?

 

Actually 700rpm is correct, 1000rpm is too high. Sounds like it took a while but it fixed itself!!<IMG src=smileys/smiley4.gif border="0">

 

It shouldnt have dropped the idle speed! My 87 200 did that and when i took it to an engine machining mechanic he siad that it could have a bent valve or simply needs a valve job. He explained that due to the engine having 110thou miles it would have worn the engine slightly causing it to gradually idle lower. But doing a valve job cures this problem by uping the compresson of the engine giving better starting and running from cold and much more power. My cars cylinder head had also got knackared valve guides so i got them to fit titanium ones and re-seat all the valves. It also has had a bent exhaust valve of which i replaced. The head was also skimmed and the valve guide oil seals replaced which has completely stopped the oil consumption prob it used to have. It resulted in a total bill of around £400 or $600ish but for that the cyl head was as good as the day it was asembled on the car at mb factory! But it was worth it as the car runs beutiffly since. It may seem drastic but it will restore the idle speed and leave the car running much better as it did for mine!