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  #46  
Old 01-08-2013, 11:05 AM
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Location: Jacksonville, FL
Posts: 474
I have owned vehicles with each example of the ICV. Both the Euro 500 and Euro 380 experienced high idle rates at different times. As stated in an earlier post, after confirming that all other systems which could cause a high idle rate were good (including idle air hoses that attach to each injector heat shield and run under the air flow meter), cleaning/replacing various ICV's with US/Euro versions and rebuilt idle computers, what solved my problem was a new idle computer. From my own experience I have little faith in the rebuilt units being able to pulse at the necessary rate or amperage. Also, replacing the hollow bypass plastic line with the solid one (or just removing the tube and plugging both holes in the rubber hoses) will reduce the idle rate somewhat. If I had access to a used 380 Euro valve at a decent price it would be worth looking into but for the price of a new 380 ICV, Euro or US, I would not risk it. Keep in mind Mercedes went through several iterations of vacuum advance/retard on the US 380 engines. According to the 1983 tech data book, 1981 saw vacuum retard at idle and advance at higher rpm, 1982 saw only advance at higher rpm and 1983 and beyond saw advance at idle and higher rpm. Big difference in idle rates based on these parameters but supposedly US 380's used the same ICV's throughout. If your engine is supposed to have vacuum retard at idle make sure it does. This substantially reduces the idle rate. Another thought is to consider buying a new idle computer as a loaner to be used for testing or borrowing a known good unit. New idle computers are a relative bargain compared to any new 380 ICV. Mark

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  #47  
Old 01-11-2013, 07:42 AM
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Quote:
Originally Posted by hookedon210s View Post
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.
Thanks for the additional info, Mark. But I'm not sure which line you're referring to here. Could you please clarify this please?

Thanks
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  #48  
Old 01-11-2013, 01:41 PM
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There is a bypass tube that connects between the two molded rubber pieces that the ICV sits between. I have attached pictures of the two molded rubber pieces and there is a picture of the pinched off bypass tube (PN A1169971652) in post # 4 in the following link M117 air hose ID help (Apparently I can't attach the same picture to this post since I already attached it the other post). The molded rubber parts are part #'s 77 and 83 on the attached pdf and the pinched off tube is part #86. On some applications a hollow tube is substituted for the the pinched off tube in which case more air is permitted to bypass the ICV. Substitution of a pinched off tube for the hollow tube eliminates this bypass air and, in a system that is otherwise flowing too much air, will reduce the idle rate.

Mark
Attached Thumbnails
Idle Speed Air/Control/Slide Valve Confidence Check-1160941291%5B1%5D.jpg   Idle Speed Air/Control/Slide Valve Confidence Check-1160941391%5B1%5D.jpg  
Attached Files
File Type: pdf ICV Picture.pdf (70.6 KB, 284 views)
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  #49  
Old 01-14-2013, 09:15 AM
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Thanks for the pictures, Mark. However, none of the ICV's we listed have that bypass tube.

Considering the possibility of using a Euro ICV, do you happen to know what the effect of using that or a US ICV with a Euro ICU would be?

Just a thought.

DD
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  #50  
Old 04-29-2014, 12:48 PM
merc with a..Benz
 
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Location: far,far nor cal
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Quote:
Originally Posted by dpetryk View Post
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!!!
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  #51  
Old 11-20-2018, 02:13 PM
Doktor Bert's Avatar
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Interesting thread. I haven't picked up a wrench in years, but occasionally see what perils others are dealing with. Notwithstanding all the good points raised herein, with regard to vacuum leaks, voltage values and the known problems with idle speed regulators, I should also like to add that in many cases, I frequently saw a worn/mal-adjusted idle switch. This often results in everything else being replaced simply because of the difficulty in accessing the idle switch. At any rate, when I was working on MBZ's with the CIS/IAC systems, I used the BMW-style idle air control valve with frequency adjuster...
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  #52  
Old 01-17-2019, 09:44 PM
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Hi Folks,

I have been stuck on this high idle and finding information about the actual ICU and the ICV functionality in detail for a while. This is an informative thread but I need to find more information.

OVP has battery voltage on both sides of the fuse and pin 2 on ICU has battery voltage. I have tested the ICV by applying 12vdc directly and find that it drops my rpm to a stall. I am confident that the ICV is functioning but I do not know how well under lower pulse voltages. I have two ICU's, one is original from vehicle and the other is a used unit. Both have same part numbers - 002-545-33-32. I removed the back of the wire harness on the ICU to measure readings at the pins.

Current original ICU
PIN:
2 = 12v (battery voltage)
4 = GRD
6 = 12v (bv)
8 (not sure what to measure but there is no voltage)

pins 1 and 5 control ICV

1 = (no voltage to ground or to pin 5) but I get battery voltage to + batt terminal as if pin 1 were a ground
3 = 6.25~6.4 volts
5 = same as pin 1
7 = same as pin 8
9 = same as pin 8

The other used ICU that I tried had the same pin results except that across pins 1 and 5 there was .25~.30 volts.

Still have the high idle. I checked all the temperature sensors and grounded/jumpered them to be sure. Looking at other suggestions, I also replace the three transistors on the original ICU board and re-soldered what looked like a couple of cold joints, there was no change.



It would be great to have a detailed component/electrical schematic of the ICU. I have not found a reasonable price for a ICU yet, otherwise, I would just purchase another as well as an ICV. I have two ICU's here and no reason why I can't get one to work.



I did some further testing with this. I tested the voltage across the ICV pins with harness connected and showed .30 volts. Disconnected the ICV harness and went across the harness that showed 0 vdc. It did not matter if the engine was cold or hot. I changed out the ICU with another I had, same readings except the only difference was that the ICV harness showed battery voltage when disconnected.


I also started the engine cold and hot with the ICV wire harness connected and disconnected, no change, still idles at 1500. I did a quick and sloppy smoke test to look for large leaks, no leaks.



I am not sure what voltages I should be seeing at the ICV and ICU with harnesses connected/disconnected. Though, I did see the voltage at the ICV is supposed to be about 5 volts which I am not getting. I have to find out if it is a malfunctioning ICU or if the ICV is dragging down the ICU. I have tested the ICV with 12 v and it seems fine but the resistance across the pins is out of range at 10~11 Ohms. With the voltage so low at the connected ICV harness, maybe the ICV is resisting too much making the ICU work too hard. I will try to check current.





Does anyone have any ideas, information or direction to share?

Much appreciated !!

'85 500 SEL 117.963
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  #53  
Old 08-11-2020, 09:18 PM
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Quote:
Originally Posted by dpetryk View Post
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.
This tip seemed almost to good to be true, but it was exactly the right thing. Never EVER would have figured it myself, and the manual wasn't forthcoming with this information. Thanks so much for putting it out there.
Brian
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  #54  
Old 08-12-2020, 11:46 AM
dpetryk's Avatar
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Join Date: Sep 2001
Location: Houston, Texas
Posts: 1,072
camel125,

I would give up in trying to analyze the problem from the electronics side of things. I say this because I am en electronic engineer and I tried to do what you are attempting.

I came to this conclusion;

The bottom line is this; for whatever reason the electronics has limited or insufficient authority over the ICV and cannot control the idle properly if the basic mechanical parameters are not in a specific range.

So just do as I suggest and adjust the mechanical parameters and it will solve the problem. I have 5 of these cars and it worked on all of them. No need to get into the electronics unless it is defective to start with.
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  #55  
Old 08-17-2020, 11:33 AM
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Just bumping this to say that Dpetryk's method worked for me. I had cleaned my ICV out and got my idle to drop from ~1250 to ~1050. I started messing with other stuff like pulling the ICU relay and the OPV to see if it made my idle spike which pulling both of them did. After that my idle was back up to 1250-1300. I couldnt find a schematic to test the pins on the OPV or ICU and i didn't want to just buy new ones so i said why not and tried Dpetryk's method. My ICV was recessed 1.07mm i pulled it out flush and my idle dropped from ~1300 to ~750. The idle stays steady at stop lights i was worried trying this method if something else was wrong like the ICU it wouldn't be able to compensate and stall while at a light or something but seems to work fine.

One problem is on start up until it heats up a little the engine will fluctuate Rpms jumping from 750-1000 not staying steady and you cant get gas to the engine it wont react. I think that's a separate problem being my plugs are getting dirty from letting it idle so much testing other stuff im not that worried about it.

Next time i go past a parts yard i will probably pick up all the pieces the ICV/OPV/ICU just to have extras in-case something pops up but for now its working great.

Edit:cleaned the plugs as i had the same exact problem before but it did not help this time. So im not sure if this is related to what i did with the ICV but hot or cold when i start the engine the Rpms fluctuate between 750-1000 and i cant get any power to the engine. After a minute or so everything is fine.


Last edited by Whaling; 08-17-2020 at 03:00 PM.
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