My 87 260E has an extremely eratic idle. Even when it is cold or warm. When it is running sometimes it runs o.k. and other times it is barely running at about 500rpm and it stalls sometimes to. If I let it run at 500rpm it will eventually catch after several minutes and run smoothly. When I start it the same thing happens, it will barely run at about 500rpm and after a few minutes it will raise to a normal cold idle. Does anyone know what I can try to do to fix this.

Hi Todd
You might have a bad Air flow sensor or
bad overload protection relay.
Have a MB tech help you test it.
I seen lots of then gone bad.
good lock

where is the air flow sensor located? how easy is it to replace it? do you need to have it on the lambda machine to regulate air/gas mixture?

The air flow senser is attached to the side of the air flow housing. This housing is beneath the air filter & the fuel distributor is mounted to the top of the housing. On most Mercedes this sensor cannot be replaced by itself, only comes with the housing. When this sensor goes bad most engines will have a very erratic idle(common failure). Because of the intermittant nature of this problem a lot of M.B. techs overlook this problem, not easy to Diagnose & repair.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH