w116 450 sel over revving

[andyshergold]

i wondered if anyone could advise me as to the possible cause of my 116 revving and maintaing quite high revs even when its warm,if i boot it hard the revs drop but are still above what i would consider normal, they drop again when drive is engaged but it still seems high,all suggestions welcome as saturday is garage day !!

 

[grober]

Sounds as if your fast idle throttle bypass is not closing as it should should close when the engine is warmed up but they can get gummed up. Same applies to the throttle plate/or associated lever mechanism

 

[Ian B Walker]

I don't know how relevant this is but we have had a 500SEL that would not tick over at anything less then 2000 rpm. Disconnected all the linkages etc with the same effect. In drive it seemed ok. Our solution was the change the ovp relay. Cured our problem.

 

[nick mercedes]

Have 116s got OVPs?

 

[Ian B Walker]

Have 116s got OVPs?

I am not sure. Obviously someone here will confirm that.

 

[andyshergold]

i will have to investigate further,not sure about ovp either,tried wd40 on the linkages but that didn't work,where will i locate the FAST IDLE THROTTLE BYPASS is it the same as the IDLE SPEED ACTUATOR ,i have a complete 116 mb service manual,so i'll look in there aswell.thanks for the most helpful suggestions

 

[grober]

i will have to investigate further,not sure about ovp either,tried wd40 on the linkages but that didn't work,where will i locate the FAST IDLE THROTTLE BYPASS is it the same as the IDLE SPEED ACTUATOR ,i have a complete 116 mb service manual,so i'll look in there aswell.thanks for the most helpful suggestions

Its sometimes called the auxilliary air device is is usually plumbed into the rubber pipework surrounding the main fuel injection unit somewhere. It will have an electrical plug on it.

 

[andyshergold]

thanks for the helpful info,i will get the bonnet up in the morning