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560SEC / 850CSI / 525i
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Discussion Starter #1
Was thinking about changing the hoses on the ICV (yes I know I can buy new ones from Merc cheap, but cant do that right now) and I have some large OD rubber hoses that will fit from the manifold to the ICV however they dont have that little plastic breather pipe.

Anyone know the purposes of the small rigid pipe on the ICV rubber hoses (it bridges one from the other, I guess bypassing the ICV)?
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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It plugs the holes in the elbows. It doesn't do anything. If not tight it will leak air and you will have a vacuum leak. One end is crimped shut.
 

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Discussion Starter #3
Mine is definately not crimped shut..? Why would they design holes in the elbows at all if they would stick a seal pipe between anyway?
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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Hi

"Why would they design holes in the elbows at all if they would stick a seal pipe between anyway?"

Sounds as if you might be grumbling?

Please post a pic so we might see the offending hoses... ?

Cheers, MBL
 

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Discussion Starter #5 (Edited)
Lol, does it now?

There are two rubber hoses or fittings on the ICV, one from the Throttle body and one going to something else. Those hoses connect the ICV into the airflow however they themselves also have a small pipe connecting them directly (which would bypass the ICV?). My pipe was not crimped at one end as described.





Since posting I rigged up some nicer rubber boots for the ICV myself, without this little pipe. Seemed to work fine, however made no difference to my high idle (1k RPM) problem. Infact Ive now repaired 6 damaged pipe leaks and had no change to Idle speed, making me wonder just how big a vacuum leak you need to actually have any meaningful impact. Economy gauge is to the left as it should be.

I think next port of call is the Idle Control Module (relay) as I changed the ICV, cleaned throttle plate, working Airflow meter etc. ICV is getting 4.8v at idle and if I give it 12v it stalls. Im thinking 5.2v would be perfect idle speed.
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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Sounds like you need to clean the ICV. soak it in Electrical cleaner overnight or longer and spray inside of the ports until it runs clean. if clean or new, then the Air/Fuel mixture may be incorrect.
 

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Discussion Starter #7 (Edited)
I did do that to my ICV (no change) then I bought a used but sold tested good (and it does look mint in fairness) ICV, performed the same, still approx 1000rpm. I tried adjusting the Fuel/Air mix screw (in front of the CIS), CCW made it stumble, CW didnt do much. Is there some other way of adjusting?

FWIW, I also changed the OVP already too. What is the correct voltage at idle for say 600rpm with AC off and out of gear? I get 4.8v which kinda seems ballpark correct, but clearly 1000rpm idle isnt. Disconnecting ICV and it goes to 1600 as expected.


EDIT: To answer my original question, I found this on another forum, why the little pipe is there:
What I did was replace the two rubber pieces that meet the IAC (idle air control) valve. Or whatever Benz calls it. What I did not have was the little plastic tube that bypasses it to prevent a stall if the valve closes fully. So I used a barbed pipe that I cut to fit.
Apparently its not on all years or models (some are crimped).
 

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Do i understand correctly that this small connecting pipe in your car is empty from inside and your idle is a bit high (at 1000 rpm).

I had the same issue with high idle. My car came from Japan and it had a green pipe that connected. The car was originally sold in Austria. A knowledgeable friend of mine suggested that this pipe could be a way to adjust idle for different heights (i.e. if you live in mountains you have a hollow pipe, if near the sea, it will be closed). I think try to close the pipe (or put two bolts in both ends as i did), you might get your idle lower. My idle rpm dropped by ~150 afther this change.
 

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Mine has a tube in it. It's a Swiss car. Which means you'd need a variable tube :D
I'll check out where it goes tomorrow and post.

Pete
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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Mine is crimped. I do remember that on Blue Bird, I had the same problem, open pipe, and I closed the pipe off and made sure there was no leak at the junctions of the elbows. That closed a small vacuum leak.
 

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Discussion Starter #11
Yes, mine was an open pipe with the stock ICV rubber piping, however Ive just put in my open rubber ICV piping, no breather pipe, no difference at all to idle! I dont get it, lots of small vacuum leaks now fixed, but idle never changes. I never got the sky high 1200rpm+ big leak type idles others got either, even when vacuum on Economy Gauge was sitting 2/3 to the right, idle was 1000rpm.

I know its not true, but from my experience I could conclude vacuum leaks dont influence idle on this car!? :confused:


I notice with my (no breather pipe) soft rubber fittings I installed going to/from the ICV if I pinch then hard the car will cut out. Im guessing with the breather pipe this wouldnt happen.

My next steps are:
  • Coolant Temp Sensor
  • IAT Sensor
  • Transmission Vacuum module
 
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