Idle adjust on 87' 420 SEL
 

Greetings

Can anyone tell me how to adjust the idle on a 420 SEL? It idles at about 500rpm while in drive and 600 in park. In drive the idle is a little rough and if I press the pedal a little to raise the rpm to about 650RPM its smooth as silk. So I would like to raise the idle a touch but can't seem to find the adjustment. Any help will be appriciated.

Thanks
bob:confused:

The idle is electronically controlled and as such is not adjustable. There are a group of cars (years) that can get 50rpm higher by grounding pin 10? on the idle controller. Check the archives as there are posts giving the years involved and specifics on circuitry.

Well I did a search and nothing came up fo rthe 420.

Anyone no if this can be done on the 87' 420?

Thanks:mad:

Check for rough idle on this board
 

Go check for rough idle on this board. I had somewhat similar adventures on my '89 560 SEL.

Well try these instructions. They appear to me to fit your car.

Thanks Steve

I will try that as soon as I get home.

bob

:)

I found the Idle control uni and grounded pin C. I will let you know how it performs.

Bob,

You can also go a long way to smoothing the idle on CIS cars by using Chevron gasoline.

Peter