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1984 500SEL
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10 Posts
Discussion Starter · #1 ·
Hello all, I've done a search and now I'm totally confused [:(] I have a 1984 500sel, the idle "stumbles" most of the time when its at op temp, the oil gauge also jumps around while its doing this... thought it was due to rpm dropping then going back to normal but after reading some posts I'm not sure now... something about it being tied into the idle circuit. Anyway it also stalls sometimes when you come to a stop. From what in can figure out I need to clean the air valve and check the elec. box for cracked or cold soldier joints. The elec box is the easy part once I figure out where it is as I've fixed many "junk" Volvo overdrive relays in the past. I guess I'm asking if I'm on the right track and is there anything else I can do?

Thanks in advance for your help:

Rob
 

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Moderator
1991 500SEC Euro, 1987 560SEC Federal
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5,563 Posts
Hello Aarn,

Well if you can brave the 'Volvo Overdrive Relay Syndrome', you're gonna fit in just fine here! [:D]

I'll bet the oil gauge reading is very much connected to the evasive idle speed. Your car might have a compound problem... What happens if you spray each injector holder (engine running)? If the speed changes, smoothes out or drops off.. you know there is an vacuum leak..

Here's the box location.......

Good luck, MBL
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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44,585 Posts
What shape are your rotor, distr. cap and wires in? What do the sparkplugs look like? Has the timing been checked? Any vacuum leaks or leaks around the injectors? How old is the fuel filter? If fuel related, adjusting the air/fuel mix should take care of the stalling problem. It would help to know what you have done so far. The 'search this forum' box has write ups on all of this, including how to clean the idle control valve. Good luck.
 

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1984 500SEL
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10 Posts
Discussion Starter · #4 ·
Thanks for the Pic MBL... all the "tune-up" parts are great. I've sprayed all injectors and vacuum lines with card cleaner and WD-40 just to double check, good there... filters are newer (last 6 months). The car has had the idle thing since we bought it last year, just started stalling when coming to a stop, when I did all the plugs etc I thought the 600ish idle (by the tach) was kinda low until I looked it up... the car only has 117k on it and runs like new except for the idle. The valve is soaking right now, when I pulled the plug on it the idle inceased which if I read the posts I searched correctlly means its working. I'll pull the box and redo all the joints tonight just for good measure.

Thanks again
 

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1991 500SEC Euro, 1987 560SEC Federal
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5,563 Posts
Good Luck!

What happens if you unplug the Ox Sensor (warm running engine)?

Smithfield Hams........................ Man, I remember those as a house gift produced by my uncle from VA, several times during my formative years.

Mouth watering pretty good right now, MBL [:D]
 

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Premium Member
Tribute 500SEC AMG Widebody
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6,242 Posts
quote:
48hp - 3/4/2006 1:33 PM

Per Factory Service manual V-8 Engine 116..96 & 117.96:

Checking electric activation of idle spead adjuster (ICV)

Engine - operating temperature.
Ignition switched on.
Pull coupling from idle speed adjuster and measure voltage.

Readout approx. 12v then

Checking regulation of control unit

Engine at idle at operating temp. Plug on couple at idle speed adjuster in a manner that voltage can be measured on plug.

Readout 5v +-1 then

Check idle speed adjuster

Engine at idle.
Simulate coolant temp <42 degree C, for this purpose pull coupling from temp switch and bridge. (located at rear passenger side on top of manifold)

Idle speed increases to approx. 750/min.

End of test

Any other values then those described above suggest a faulty control unit (located at firewall)

If a faulty control unit is found, nowhere within the Mercedes Manual does it suggest this method but others have suggested this and it worked for me. Remove the control unit cover and lightly twisting from side to side while engine is running. Idle should drop to normal speed once twisted in a manner that effects the potential poor solder union. Heat each and every connection, adding a bit of solder to each point. My idle is now on the money.

Hope that helps.
 
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