Idle Speed Air/Control/Slide Valve Confidence Check

[dpetryk]

Here is the adjustment. - You move it inward to increase the idle speed and pull it out to reduce the idle speed. When moving it make small movements. I use a flat tip screwdriver to pry between the nut and the housing to pull it out. I use a vise to push it in. The screw is a 10-32. It is not the right thread but it will hold. I do not screw it too tight for fear of trashing the threads inside the brass thing in the valve. I just make it hand tight but be sure it is seated. I could not find the proper screw to fit it. The 10-32 works great for me. Remember just small adjustments.

[dpetryk]

BabyBlue, while you are in there you want to replace all the rubber donuts between the manifold halves because these harden up over time and leak causing a high idle condition. Also any other seals that are exposed to vacuum.

[dpetryk]

My idle speeds are 700 in neutral and 650 in drive. On all my cars.

[BabyBlueBenz]

Thanks for the great pictures and your idle speeds, Dave. That's an interesting approach on adjusting the ISAV. I concur with your suggestion regarding making small adjustments to it. Observing my ISAV with power applied, I saw little more than a 1/4 inch in its range of motion.

I didn't expect to have to take off the intake manifold to get at the throttle! The service manual pages indicate that just the Mixture Control Unit with Air Guide need be removed (07.3-225) as a prerequisite to removing the Throttle Assembly...and I don't really want to remove that unless its necessary.

If I have to break the coolant system open, then I'm in Timing Chain & Guides replacement territory. I was nervous enough just considering disconnecting all those wires and fuel lines to access my faulty switch.

Is there not enough room to reach the Throttle Valve Switch with one of these?

[dpetryk]

I'm sure you are right - you don't have to remove the manifold to get to the switch. I had a lot of nasty residues and some liquid on the bottom half of the intake manifold so I decided to clean up everything. Garbage tends to collect in these types of "uphill" manifolds. I was fighting vacuum leaks and I wanted to be sure I replaced all the potential sites for leakage.

[450slcguy]

Originally Posted by dpetryk

BabyBlue, while you are in there you want to replace all the rubber donuts between the manifold halves because these harden up over time and leak causing a high idle condition. Also any other seals that are exposed to vacuum.

Great pics. I'm fairly convinced that is the cause of my high Idle hell as everything else has been addressed. Come some warmer weather, that's my next project.

[mbboy]

Originally Posted by dpetryk

Here is the adjustment. - You move it inward to increase the idle speed and pull it out to reduce the idle speed. When moving it make small movements. I use a flat tip screwdriver to pry between the nut and the housing to pull it out. I use a vise to push it in. The screw is a 10-32. It is not the right thread but it will hold. I do not screw it too tight for fear of trashing the threads inside the brass thing in the valve. I just make it hand tight but be sure it is seated. I could not find the proper screw to fit it. The 10-32 works great for me. Remember just small adjustments.

I was going to try this to reduce my high idle, since I've tried everything else, including changing the ICU, checking for vacuum leaks, adjusting the linkage, etc.
However, I assumed that the rubber ring this screw goes into was empty and threaded, but it isn't. The ring has a little brass cap in it. So, before I ruin my ICV, I was wondering if you change the idle by using this screw to push the brass cap down?

Thanks very much for any help anyone can give me on this procedure.

[dpetryk]

The screw is threaded into a brass piece which is threaded. Its not a rubber ring as you said. It may look like rubber in this photo but it is not. The brass part slides inside the aluminum part inside the 3 spokes you see in the photo.

Maybe your ICV is different than the one pictures here.

[dpetryk]

IIRC there was some sort of cap over the hole. Remove it and see what you have underneath.

[mbboy]

Originally Posted by dpetryk

The screw is threaded into a brass piece which is threaded. Its not a rubber ring as you said. It may look like rubber in this photo but it is not. The brass part slides inside the aluminum part inside the 3 spokes you see in the photo.

Maybe your ICV is different than the one pictures here.

Thanks for getting back to me Dave. Attached is a picture of an ICV that looks like the one that's on my 1981 380sl, as well as the one you showed. The part # is 0001411225, and it's used on the 107's with 116 960-963 engines, as well as the 117's with the 116 963.

As you can see, there's a little brass plug at the bottom of the inner ring, which looked to me like it was not threaded and made of rubber. I'm going to take it off again later just to make sure and, hopefully, after you've responded to this message.

Assuming that it is unthreaded rubber, however, do you think I could still use your technique to adjust my idle, assuming that the screw is going to hit that little brass plug? Or, do you think there might be another way to pull the ring out?

Now, I did notice that there's another ICV on Ebay, part #0001411625 that superficially looks exactly like mine, but it's used on 116.964 and 965, and the 117 964-968. However, I haven't been able to tell from the pictures whether the ring on that one has is different from the ring on mine. But maybe that would account for the discrepancy I'm trying to resolve?

[dpetryk]

HArd to tell from the photo how its put together. I would toss out the possibility that the part that has the 3 spokes might move inside the aluminum part. So that entire assembly of the spoke part and everything attached to it moves. My type of valve is press fit so adjusting it takes a good grip on that brass piece. It may be that your type needs to move the entire center assembly including everything attached to it.

Just an idea.

[hookedon210s]

All good advice in this thread. On my 1983 380SE (euro) I had high idle problems for quite some time. Note that the early Euro ICV's are different than the US versions since there is no vacuum advance at idle on the early US cars so the US versions have to flow more air to idle at the correct speed. This difference presents an opportunity to use a Euro ICV to reduce airflow and hence the idle rate of a US engine. Also note that the absence of vacuum retard at idle due to vacuum retard can diaphragm leaks on the early US cars can cause a high idle. To continue, I cleaned/ replaced the ICV multiple times, replaced the control unit a couple of times with rebuilt, checked for vacuum leaks, etc. without totally resolving the issue. In desperation I finally bit the bullet and bought a new control unit from the dealer and solved the problem. My assumption is that the rebuilders generally do an incomplete job which leaves the current handling/pulsing abilities of the control unit below what is required to maintain the proper idle. Also note that the revision to the vacuum lines substitutes a solid (closed) vacuum line which reduces idle airflow slightly and will in turn reduce the current/pulsing requirements of the idle control system. Mark

[daimlerdude]

Originally Posted by hookedon210s

Note that the early Euro ICV's are different than the US versions since there is no vacuum advance at idle on the early US cars so the US versions have to flow more air to idle at the correct speed. This difference presents an opportunity to use a Euro ICV to reduce airflow and hence the idle rate of a US engine. Also note that the absence of vacuum retard at idle due to vacuum retard can diaphragm leaks on the early US cars can cause a high idle. Mark

Mark,

Can you tell me which models you're referring to? When I access the engine/injection section of the 380sl European model on the EPC, it says "Not valid for this model. And, AFAIK, neither the 350sl nor the 450sl had an ICV.

BTW, the part # of my ICV is 0001411225.

Thanks in advance.

DD

[daimlerdude]

Originally Posted by dpetryk

HArd to tell from the photo how its put together. I would toss out the possibility that the part that has the 3 spokes might move inside the aluminum part. So that entire assembly of the spoke part and everything attached to it moves. My type of valve is press fit so adjusting it takes a good grip on that brass piece. It may be that your type needs to move the entire center assembly including everything attached to it.

Just an idea.

After taking a closer look at my valve, I can see that the ring I identified as rubber is indeed metal, and that the little brass piece in the center of the ring is in fact some type of cap.

However, that cap is recessed and, as far as I can tell, it's sitting in a spindle that connects the ICV's outer ring to the ICV's revolving wheel. So I can't figure out how to remove the cap, especially without risking having it drop down into the ICV?

I should also note that, per your instructions, I cleaned the ICV out, even more thoroughly than I had before with brake cleaner and an electronic component cleaner. But that didn't change the idle one bit. OTOH, I could see that the outer rim of the revolving wheel still had some caked on carbon on it, which I couldn't remove.

So, that's where I'm at right now

[Deadpool]

Originally Posted by dpetryk

Here is the adjustment. - You move it inward to increase the idle speed and pull it out to reduce the idle speed. When moving it make small movements. I use a flat tip screwdriver to pry between the nut and the housing to pull it out. I use a vise to push it in. The screw is a 10-32. It is not the right thread but it will hold. I do not screw it too tight for fear of trashing the threads inside the brass thing in the valve. I just make it hand tight but be sure it is seated. I could not find the proper screw to fit it. The 10-32 works great for me. Remember just small adjustments.

MY GOD, MAN!!! Where have you been all my life?!?!? I have been searching for an answer to my "high Idle" problem and have found scattered advice (some good, some not), incomplete checklists, angry MB owners and copious amounts of frustration...until now. A trip to the hardware store for a "dpetryk air idle adjustment tool" and viola!! now she purrs like a kitten, in the factory idle range. Could not be happier without a plate of chimichangas as I am right now.

Thanks.

Thank you!

A million thanks!

May the ever lovin' light shine on you so bright you need welding glasses to get through your day!!!