another 560sl - year is 1987 - idle = 1500 r/pm

[blueshield11]

I have a 560SL from 1987. Idle is not okay at all: steady on 1500 r/pm, with cold engine as well as with warm engine.

Any idea what the problem can be here?

Thanks a lot !!

[Gurunutkins]

I am not that familiar with the 560 but it sounds like the auxiliary air valve is stuck open. I believe you have an electrical one, it should close as the engine warms up. easiest test is to grab the air pipe feeding the AAV (also called a cold start air valve) and just pinch it closed with your fingers or a vice grip with some cardboard between the jaws and the rubber pipe. if the engine slows down you have found your problem
cheers
barri

[blueshield11]

Originally Posted by Gurunutkins

I am not that familiar with the 560 but it sounds like the auxiliary air valve is stuck open. I believe you have an electrical one, it should close as the engine warms up. easiest test is to grab the air pipe feeding the AAV (also called a cold start air valve) and just pinch it closed with your fingers or a vice grip with some cardboard between the jaws and the rubber pipe. if the engine slows down you have found your problem
cheers
barri

Thanks for your reply but there is something I do not understand. I think you are giving me the right answer, but my english is not that good.

You say: easiest test is to grab the air pipe feeding the AAV (also called a cold start air valve) and just pinch it closed with your fingers or a vice grip with some cardboard between the jaws and the rubber pipe.

can you explain me a bit more. where is the air pipe feeding the AAV ? and where are the jaws and the rubber pipe?

thanks a lot,
Jan (The Netherlands)

[Gurunutkins]

Jammer Jan maar my duits in nie te goed nie!

I am unsure of the set up on the 560 but there will be a rubber air pipe coming off the throttle body or the air cleaner it will go to an electircally controlled air valve like the one in the picture (and forgive me if this is incorrect for your car) then the pipe will leave the valve and enter the block where you adjust the idle speed just after the idle speed screw.

what you need to do is pinch closed the rubber pipe going into the valve with your fingers or if they are not strong enough then clamp the rubber pipe between cardboard and the jaws of a vice grips or pliers so you stop the air entering the air valve. if you can block the air flow through the valve and the engine slows down then that is your problem.

the picture is of a AAV taken from a similar car to yours

I hope this helps

[Gurunutkins]

Jan I will send you a diagram of the car system if you PM me your email address but here is a small version the AAV is item Y6

[blueshield11]

thank you barri. I have received it and will go to work with it.

[milbroman]

Check the voltage at the idle control valve by backprobing the harness with a multi meter set to dc volts should read around 4 volts. if nothing check continuity of the black and yellow wire from the idle valve to the idle control unit using multi meter set to ohms should read open. check the black wire in the same way. if the resistance is infinite find and repair the break in the wire. if ok check for voltage on the red and blue wire in the harness at the idle control unit behind the glove box remove the lower cover and the inner cover of the glove box to gain access. if no voltage strip the covering on the red and blue and use a jumper to energize the wire from the fuse block. if this solves the problem trace the red and blue wire back to the overvoltage protection relay and check the function of the relay.