[W126 Coupe] HI IDLE

[Dick Spellman]

Hi Rich:

I have not been following this list as much of late so I don't know if a 
list of devices has been provided for you to check out.  Here are a few 
to start with:

With engine off...Check your throttle position switch (at idle) several 
times after opening the throttle a bit and letting it settle back down 
to affirm it shows 'closed' using an ohm meter.  You can check the wide 
open throttle (WOT) as well but, it's not relevant to your high idle 
complaint.
Check your overvoltage protection relay fuse and supply voltages to 
confirm it's working as it should

I see the ICV has been well covered and I've done the fix as Mike Ramay 
laid it out for me one Saturday morning by phone on a 300SE.

Pull the Idle Control Module (ICM) from the center of your firewall, 
remove the cover-exposing the circuit board and with engine running, 
board in hand and connected to the plug-in harness use your thumbs to 
pressure components and flex the board slightly in different spots to 
see if the idle settles down or lowers/raises with the thumb pressure.  
If you see this result, the board needs to be replaced, if not move on 
to other checks.  There are several other more involved checks on the 
fuel side that may be needed if the electrics check out.

I believe you will find the Idle Control Module (ICM) is a likely 
culprit for your description if the ICV checks out for resistance and 
you've confirmed the valve is moving freely.  A rebuilt unit is about 
$155 US and comes with a thumb screw idle adjustment to set idle 
'purfectly' on installation.  The OVP must be in perfect working order 
to prevent voiding of the 3 year warranty on the new module.

-\Dick

richard jaffe wrote:

> Hello All,

>  

> I just replaced the original steel fuel injectors with brand new shiny 

> brass ones along with new seals, holders and air tubes. Also put in 

> new Beru spark plugs. Engine now runs nice and smooth but now have 

> intermittent high idle. Tried cleaning out the idle control valve with 

> carb cleaner with no appreciable effect. Do I need a new idle control 

> valve or is there another culprit to hunt down?

>  

> Rich Jaffe

> 85 500 SEC Euro  259K

> 83 300 SD          192K

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