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Old 05-28-2010, 08:29 AM   #1 (permalink)
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Date registered: Oct 2008
Vehicle: 1985 380 SL, 1969 280 SL, 1980 300 SD, 1966 Datsun 1600 Roadster, 1991 Miata
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Location of Idle Control Unit (85 380 SL)

I have been reading the threads on High Idle issues and cannot locate my Idle Control Unit. Supposed to be on the firewall, but I do not seem to see any black boxes on my firewall (on the engine side). The Fuel injection control box (and something else) are on the firewall on the inside passanger footwell. Is this what I am looking for? Sure do not want to fiddle with the wrong component.
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Old 05-28-2010, 08:50 AM   #2 (permalink)
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Here is a pic of the location of the idle control unit behind the glove box posted by another member of a forum. You have to remove the box liner.

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Old 05-28-2010, 01:11 PM   #3 (permalink)
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The idle control relay is behind the glove compartment , as the picture shows , you have to remove the glove compartment liner to access it. If you are performing test on it i found that it is much more accessible to (also) remove the lower dash cover under the glove compartment.
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Old 05-28-2010, 01:43 PM   #4 (permalink)
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Thanks guys, I found it. Not real easy to get to, but not as bad as some things I have found on this car. Wanted to know where it is because I have experienced the "high idle hell" once earlier this year, then it simply went away the next time I drove the car and has not returned, but I know it is there, and my wife will never trust it again for a road trip until I have remedied the situation. I hate trying to fix something that is working fine

Anyway, I started fiddling yesterday and disconnected the power to the idle air valve (slide valve) which of course caused the high idle, then re-connected it and it started running like crap. No amount of disconnecting/re-connecting helped. Well I obviously messed something up, but what! I checked the OVP relay to see if maybe I blew the 10A fuse, but everything "looks" good.

I have taken the idle air valve off now and am soaking it in carb cleaner and will re-assemble and see if it is still running badly. It is no longer a high idle problem, it is just a bad running problem. I will probably be asking a bunch of questions as I eliminate what it is not.

I have ordered new vaccum fittings around the valve for starts, and will replace the OVP relay, because so many people have had trouble with it. The idle air valve is an expensive bugger, so I am soaking. It does seem to open and close with external 12V put to it, so I am assuming it is OK.

I hate mysteries!
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Old 05-28-2010, 06:34 PM   #5 (permalink)
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high idle hell

Check the wires of the plastic connector to the air valve (mine came loose while chasing high idle hell, and I had to re-solder the wires).

Or pull the electrical connection, with car warmed up, test voltage across the inside of the connector (not the pins) ... should be 12V.

If that's ok, put the connection back on the air valve, but back it off ever so slightly. Then check voltage across the pins ... should be 3.75V-ish.

Do a search on "high idle hell". Thanks to the help of the members, I've managed to get past it (took a couple of weeks and an air valve (used from eBay)).
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Old 05-29-2010, 10:37 AM   #6 (permalink)
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I just experienced similiar problems with my 85 380sl . Mine was running very rough (Air slide valve not getting power), the air pump had stopped coming on and the ABS light was constantly on. Turns out it was the overload relay causing all of this. I had looked at the OL relay many times, but nothing seemed to look bad and the fuse on it had never blown. The relay has 2 spring like contacts inside and was only making contact on one side when it closed. Good luck, mine started as an intermiting problem that would reset itself by switching off the car and then restarting. It finally became a constant problem after about 2 years. Its surprising how a electrical component issue can resemble a fuel issue. If you need any further assistance contact me and i will be glad to share any information that i may have.
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Old 03-06-2012, 02:53 PM   #7 (permalink)
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Thumbs up High Idle Hell!

FINALLY! It's been ... MONTHS of searching for answers on this ... never-mind all the Windbag Bogus Bad Guesses (@ "other" forums) ...
Apparently, the COMBINATION of seemingly unrelated symptoms has lead me to "I just experienced similiar problems with my 85 380sl . Mine was running very rough (Air slide valve not getting power), the air pump had stopped coming on and the ABS light was constantly on. Turns out it was the overload relay causing all of this. I had looked at the OL relay many times, but nothing seemed to look bad and the fuse on it had never blown. The relay has 2 spring like contacts inside and was only making contact on one side when it closed. Good luck, mine started as an intermiting problem that would reset itself by switching off the car and then restarting. It finally became a constant problem after about 2 years. Its surprising how a electrical component issue can resemble a fuel issue. If you need any further assistance contact me and i will be glad to share any information that i may have."
Exactly so: When EVER My Idle kicks up to 1700 -2000 (in neutral), the ABS light comes on, when it decides to idle as it should, the ABS light is off! I couldn't get a read on what could POSSIBLY be interconnected between the two! SO! I'm looking for the "Overload Relay"? Anybody know WHERE it's located in a 1988 560SEL?
Thanks
TF
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Old 03-06-2012, 03:13 PM   #8 (permalink)
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Quote:
Originally Posted by Tony Funches View Post
FINALLY! SO! I'm looking for the "Overload Relay"? Anybody know WHERE it's located in a 1988 560SEL?
Thanks
TF
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