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Old 02-01-2011, 02:05 PM
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Talking 1990 420SEL Idle control valve

Hi gang I have a question about repair of the idle conttrol valve, other than spraying the valve to clean it. How would one change the idle speed of this valve? Can it be changed to increase the speed? thank Memory

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Old 02-02-2011, 01:03 PM
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The IAC is controlled by the engine management computer. So, you'd need to reprogram. You could try to kluge it by adjusting the throttle blade stop screw, but that would make it rev too high when in park or neutral.
Best thing I have found to smooth out the IAC rotation is to spray it with carb cleaner to get the crud out, then drip a few drops of motor oil in it.
Seems to work & last much better than the lightweight sprays.
Don't remember the exact idle speed spec, I think it's 600 in drive, an eases up a bit in neutral/park. Regardles of the engine condition, the computer will strive to hit the 600, and a good motor will run smooth as silk at that setting, maintaining it with or withour the AC on. So if it's running rough at that RPM, then there is another problem with the tune, vacuum leak, engine mechanicals, injection, etc.

DG
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Old 02-02-2011, 02:08 PM
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Red face idle control

thank you for your reply S-class, the idle is to low and I have gone threw the clean out procedure. I have another idle control valve(original) that was to high at idle, I changed to this one and it was good for a year but now goes to low and will some times allows the engine to stall on rapid slow down, as it dips below 400 rpm. I thought there was away to change the depth of the plunger to change the idle value?
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Old 02-02-2011, 04:34 PM
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one symptom of low idle is a bad ovp
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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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Old 02-03-2011, 10:58 AM
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Purpose of idle control valve is to provide extra air during period mixture is rich during cold starting. After that period ends, i.e. car is warm, it's out of the picture.
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Old 02-03-2011, 11:16 AM
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Quote:
Originally Posted by lkchris View Post
Purpose of idle control valve is to provide extra air during period mixture is rich during cold starting. After that period ends, i.e. car is warm, it's out of the picture.
I may be wrong, but I thought it also kicked up when the AC was on (to compensate for compressor drag) and when the car threatens too low an idle. Such as the power steering pump causing belt drag when under a tight turn at low idle - such as parking.

I cleaned mine up also. Helped a bit. The advice of some oil or lubricant is critical.
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Old 02-25-2011, 06:30 PM
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Check this out it details how to solve your adjustment of the ICV.

Idle Speed Air/Control/Slide Valve Confidence Check

Look at post 11 & 12.

Post 18 says how to make the adjustment.

The ICV does not affect the mixture and it is always regulating the idle speed contrary to what lkchris says.
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Old 02-25-2011, 10:53 PM
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Quote:
Originally Posted by dpetryk View Post
Check this out it details how to solve your adjustment of the ICV.

Idle Speed Air/Control/Slide Valve Confidence Check

Look at post 11 & 12.

Post 18 says how to make the adjustment.

The ICV does not affect the mixture and it is always regulating the idle speed contrary to what lkchris says.

lkchris probably should've said that the icv's critical function is to get a cold engine up and started... but it does play a role in maintaining a decent idle..

i don't see a 124 in his signature..so i am not sure what his level of experience is wrenching..

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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