[W126 Coupe] Slightly High Idle - Possible Causes

[Dick Spellman]

What year is your SEC? 

What is the condition of your Overvoltage Protection Relay?  Test this 
first.  Test your engine temp sensor that influences cold start.  And 
depending on year, you may have warm up regulator issues and then again 
perhaps not.

As for the Idle Control Module, the PC board can be removed from it's 
case and plugged back into the harness.  Then carefully with engine at 
idle grab a hold of the PC board and gently press components to cause 
the board to flex slightly.  The only caution is to not allow the board 
to contact the chassis in any way when doing this test.  If your idle 
changes up or down as a direct result of flexing the board, the board 
needs repair or replacement.

The fuel distributor plunger only needs to be removed if the seal is 
bad.  Otherwise it is best to leave the fuel distributor alone.  Is your 
idle steady at 850 or hunting between 650-850?  Did you test the 
throttle position sensor?

Good luck.

Dick

JohnJayKimrey1 at aol.com wrote:

> Dear  Larry, Neil, Tim and Anyone Else:

> I have checked for vacuum leaks and found none so far using my mytvac 

> and vac. gauge. The vac. gauge at idle reads 21 inches+ - 1/4 to 1/2 

> bar(slow) fluctuation.Is this acceptable or point to a slight leak and 

> would this give me a 300 rpm idle problem( 850 at idle)? I removed and 

> cleaned the fuel distributor,plunger and air valve mechanism. There 

> was some varnish but the plunger was working fine. I also replaced the 

> injector seals as the fuel lines were off and these I thought were a 

> possible area for vac. leaks. I also removed the cold start valve 

> reattached the fuel line and with ign. on tested for a possible 

> fuel leak-checked good. I sprayed water over the engine at idle to try 

> and detect a leak and found no change in vac. reading. I am beginning 

> to think my problem may lie elsewhere such as  the idle control 

> unit(ICU). Everyone has advised that there is no sure way to test 

> without special equip. so I guess my next step is to bite the bullet 

> and buy one unless someone can point to something else I can try.

> By the way , I really to appreciate all the advice I have received.

> Thanks!!

>

>

>

> ------------------------------------------------------------------------

> See what's free at AOL.com 

> <http://www.aol.com?ncid=AOLAOF00020000000503>.

> ------------------------------------------------------------------------

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.