1975 mercedes R107 450sl idle speed

hi does anyone know how to adjust 1975 mercedes R107 450sl idle speed.
Mine is running about 200rpm in gear and when not in gear about 500rpm.
I know you can turn a screw next to the cold start valve but when i turn that up and start the car first thing in the morning
the engine idle go's high then low high and low for about five minutes till the cold start does it job or reaches temperature.
when i drive the car she's very smooth its only when i come to a stop she's very low.
Any help welcome mem.

Hi,
would be nice if you could tell us also your name , that makes the conversation nicer .

Greets
Christian

sorry my friend its mehmet

Hi Mehmet,

that sounds like a typical problem with your auxiliary air valve. They tend to hang and thus create either the sawing effect or too low engine rpm when cold then. I have described this AAV on my other website jetronic.org

thank you dr-jet

Hi Mehmet,

do the test that I describe there by clsoing air hose on hot engine. It will tell you whether AAV is still open and needs repair.

ok will do

i did as you described i took the top hose off and the engine went even higher then lower just as if the engine was cold but when i closed off the hose half way the engine was running good then i reversed it i took the lower hose off and that reduced the idle a little but not much this was done when the engine was warm.

Hi Mehmet,

well I did not write take off the hose but close the hose by squeezing it so that air cannot pass. If AAV is closed you will then not notice a rpm change. If it is still open on hot engine, you will.

Thank you for your advice D-jet i will try again but at same time mybe i buy a refurbished or new one just for peace of mind .
But i have a friend who is going to look at it for me and will see where it go's from there I'm in no rush but thank you again.
all the best mem

Hi Mehmet,

be careful with the housing. Many people have already broken it as it is an aluminium cast. Bosch have made a repro product for the 8-cylinder engine. But it is clumsy and I was recently told that it costs 600€.

will do i will look in to it before i buy
all the best mem