1987 560sl high idle back - PeachParts Mercedes-Benz Forum

ddayme · #1 11-15-2009, 10:19 PM

Well it seems my high idle (1800 rpm) issue is back, started this morning andwon't go away! Before, (last week) I followed some advce/tips, and re-soldered connections on the idle speed control module and the high voltage relay, removed and cleaned the idle speed solenoid, and between all that it was fixed! or so I thought, maybe I missed a bad solder joint on the module, or maybe the idle speed solenoid still crudded up? The idle speed solenoid was pretty clean when i took it off, I applied 12 volts to check it's operation and even blew in one side of it to make sure it was "sealing" good when energized. Any more ideas anyone? (I'm sure I missed something, as all of you advice was expert, probably something on my part)
Any more suggestions would be just too cool! Unfortunatly I have to drive thecar to work like this, my "86 Plymouth Reliant is being used by my son for school. I'm sure driving it like this is not good and it is also a hassle/probably dangerous!

Thanks,
Dwight Daymen (userID ddayme)

ddayme · #2 11-15-2009, 11:00 PM

Addition to above: may not br related, but ever since I've had this car, 5 years, the a/c compressor would not come on unless i unplugged the conector on the temp. sensor? (it has two prongs/wires) and plugged it back in a manner where only one wire was connected to it.

Thanks,
DDaymen

mbdoc · #3 11-16-2009, 08:17 AM

The idle speed control unit is the most likely problem, if it is getting power, ground, & RPM signal at pin TD.

ddayme · #4 11-16-2009, 10:18 PM

What would pin TD be?
Thanks

mbdoc · #5 11-17-2009, 08:03 AM

TD=RPM signal from the ignition module.

Should be around 7.5-8Vdc.

If that signal was missing the fuel pump relay wouldn't allow pumps to run as well.

ddayme · #6 11-17-2009, 02:18 PM

I guess I'm confused, as I don't know where the ignition control module is. Before, I re-soldered some solder joints on the idle control module, cleaned the idle speed solenoid, and that fixed it for 3 days, then it suddenly came back. One reason I can't check the various voltages to the module/from the module is that I have no schematic/repair literature/pictures, so I am kind of working "blind", I would order a factory repair cd, but unfortunatly it is not in my budget (the hospital where I work has cut our hours down to 3 days a week!) I guess I will have to wait untill I can get a repair cd to effectively repair this problem!

Thanks for the help,
-ddayme

ddayme · #7 11-18-2009, 02:13 AM

I redid everything I did before, clean idle solenoid, go over solder joints on idle speed control module, but no effect! just that high idle. Somewhere in this website I saw mention of where you can get a re-built idle speed control module, does anyone know the name of this place? I may have to try replacing said module, and it will have to be a re-built/used one.

Thanks,
-ddayme

pmckechnie · #8 11-18-2009, 07:19 AM

Before buying anything, try this. With the engine running, move, shack,twist, push on, or pull on the plug at the idle control unit. I went through every thing you have already done and still had problems with my 500 and after doing the above, found one or more of the signals wasn't making it through the plug. I very carefully removed each wire from the plug (make a chart of wire colors to location before you begin) and close each one up just a little. Spray just a little WD-40 or contact cleaner in each hole and replug and test again. Mine has been working great now for the last 2 years or so.
This is the first thing I do now if I have problems with electronic components. It is the best way to find bad solder joints and connectors.
Good luck,

Paul

dhjenkins · #9 11-18-2009, 09:16 AM

You applied voltage to the solenoid - did you check to see if the wire you're connecting to it had any voltage coming out of it? No voltage to solenoid = high idle.

ddayme · #10 11-18-2009, 09:58 AM

Yes, I checked the voltage to the solenoid, it was only .008! not right, I,m sure.

workerunit · #11 11-18-2009, 12:52 PM

Bad OVP relay??

ddayme · #12 11-18-2009, 03:57 PM

Re-soldered it, that was one of the things I did, but Maybe I missed something, I will remove it again and check the solder joints. Wish there was a way to check these out without replacing them/swapping with known good ones!

mramay · #13 11-18-2009, 04:14 PM

Quote:

Originally Posted by workerunit

Bad OVP relay??

Bad 10-amp fuse in the OVP red-topped unit?? BTDT, $1.00 part.

dhjenkins · #14 11-18-2009, 07:12 PM

Idle control unit just might be bad. Just because you re-solder connections doesn't mean the guts are going to come back to life.

OVP could be bad, too, but you should be getting an ABS light. Don't just visually check the fuse on it, either - ohm it out. I've seen plenty of fuses that look good that were "popped".

Some of the inputs into the ICU include vehicle speed, rpm, engine temp, compressor enable, idle input, and most importantly - ground. Bad/dirty grounds cause more "strange" problems than anything else.

ddayme · #15 11-19-2009, 12:49 AM

When I re-soldered the idle control module, the car worked for 3 days, but that may have just been a coincident. I checked the fuse on the ovp with an ohm meter, it was good, maybe there is a bad ground somewhere< any ideas where to look? as far as the anti-lock light it does not light up at all, just an unmarked light next to it. I had read about a ground by the coil, but wasn't sure just where that ground was.
Didn't get home till late, didn't even look at the car today!