cc260E

I would like to know if the air necessary to the engine at idle is going only through Idle control valve or through throttle body?

Engine is M103 on 260E 1988 euro

Thanks for your help
I like to know how the things work

bicylindrico

I will only respond because I gave advise to you on this subject before. I think if you adjusted the flap the way shdoug described previously and you are still experiencing idle problems, then you need to start looking elsewhere. You should be able to make very small adjustments over 20 minutes and know if you are making any progress. MOST of the air entering the engine at idle will be through the idle air valve and ALL the control will be through the idle air valve. There would have to be some amount of air pulled through the flap but it would have to be pretty small.

The idle air valve has the ability to increase the idle significantly. I have seen them running the engine around 2K RPM so if you are having an issue with a very low idle, that's where I would start. I still put a strong emphasis on having the idle switch functioning correctly. The only way to know is to get out your DVOM and check it. So, I guess that's the first place I would start.

I am not sure what you're wanting to hear.

cc260E

thank you bicylindrico,

I already messed the flap stop screw by ignorance.

Now I am trying to get back to the correct adjustment of the stop screw. Could not find the procedure anywhere. Then i did it by little movements ( by the way the screw is nearly unaccessible)

With the present adjustment, the engine starts even cold but with RPM below 400, then silghtly increases with temperature, then oscillates between 40°C and 80°C. Then is smooth but sometimes at 500RPMs and sometimes at 650 as per specification.

That why I wish to know if the flap should be almost totally closed. Wich would mean that all the air needed by the engine flows through Idle Control Valve.

I post the picture of a throttle valve and screw on the left bottom side

shdoug

Unfortunately, the service manual gives no provision for adjusting this. There is no information about theory of operation with the idle speed, either. In the past I have used this adjustment to set the minimum idle speed and then let the idle speed control valve do the rest.

If the idle speed is too fast, adjust the plate closed just enough to decrease the idle to proper range. It sounds like you may have a bad idle control valve. Your description indicates that the valve is never opening.

cc260E

thanks shdoug,

Unfortunately as you say the manual do not say anything on this adjustment.

ICV has been cleaned and is making the click noise.

In my case, the idle is too low, and I messed up the screw adjustment.

the idle swith has been controlled (I made a harness with a led that lights when closed and another one for full throttle)

Please see my post above.

shdoug

The valve may be clicking, but be internally screwed up. Have you tried a different ICV, just for kicks? I had one of these valves on my V.W. Rabbit and it did the same thing yours did until I turned an adjustment screw that I found inside one of the ports. I had no idea what I was doing but found that the screw caused it to start opening when cold and the engine idled perfectly after that.

I doubt your has such an adjustment, but my story demonstrates that even though the valve looks and sounds functional, it may not be. I would think you could find one of these at a Merc graveyard or e-bay though I've never looked.

I just though of this. Put a piece of hose in place of the valve and see if the idle is high. It should be. Also, can you suck air through the valve? If not then it is obviously not opening.

Have you tried hitting it with a hammer? It probably wouldn't make it any worse and might fix it!

bicylindrico

Great advise! This also gave me an idea. You could just install a plumbing spigot and have variable idle control.

If it appears to have any carbon in there you could douche it down with intake cleaner as you plug-in and unplug to clean her out.