How does the Idle Control Valve Work? - PeachParts Mercedes-Benz Forum

slk230red · #1 02-24-2009, 09:24 AM

Quote:

Originally Posted by ps2cho

Where would I attach a DMM to find the currents?

Plug your meter (in mA mode) into one side of the connector, it has to be in series. I designed a male/female plug for this purpose. Usually a problem in the ICV circuit is high idle.

But, on to your misfire problem. As pawoSD stated, your problem is more likely to be ignition related. Can you describe your misfire condition....is it a miss at idle that clears up when you accelerate?

Of course the obvious things are: rotor, distributor cap, spark plugs/wires, ignition control module, etc.

ps2cho · #2 02-24-2009, 11:44 AM

Quote:

Originally Posted by slk230red

Plug your meter (in mA mode) into one side of the connector, it has to be in series. I designed a male/female plug for this purpose. Usually a problem in the ICV circuit is high idle.

But, on to your misfire problem. As pawoSD stated, your problem is more likely to be ignition related. Can you describe your misfire condition....is it a miss at idle that clears up when you accelerate? yes exactly

Of course the obvious things are: rotor, distributor cap, spark plugs/wires, ignition control module, etc.

New OVP
New Coolant Temperature Sensor
New Voltage Regulator
New Alternator
Injector's+Seals (previous owner + smoke tested)
New Fuses
Non-Resistor OEM Bosch H9DCO's
New Bosch Ignition Wires (checked for arching as well)
New Distributor Rotor + Cap + Housing
New Fuel Filter
New Breather Hoses
Used Fuel Distributor
New Ignition Coil
Used Fuel Pressure Regulator
New O2 sensor
Used EHA Valve
New Motor Mounts
-- Head work done yesterday:
New Head gasket, intake and exhaust gasket, front timing cover gasket.
Head skimmed and pressure tested
New Water pump.
New Valve Guides + Seals
-- Smoke tested for leaks
-- Compression is 185psi across the cylinders
Swapped Jetronic Brain /w used one
Swapped Fuel Pump Relay /w used one
Swapped Cold Start Valve /w used one
Swapped EZL /w used one

^As you can see I'm not sure what is really left. I'm going to test fuel pressure next I guess.

In bold above...but yes exactly what you said. It clears up on acceleration. I was in my dads old Buick Wagon the other day and I felt a misfire on acceleration for the first time -- Mine does not have this! Idle only.

pentoman · #3 02-24-2009, 11:54 AM

The ICV of an M102 (almost certinaly identical) has a 'zero' position (i.e. if you disconnect it) of slightly open. This means that if the wiring system fails then the idle control valve will be left slightly open ensuring your car idles ok if a little high. This information may help you diagnose.
I think that a little current to the ICV closes it up, but then applying more and more pushes it past that point and on to opening it right up.

You can squeeze the pipes going into it - the idle will be caused to dip but the engine should respond by opening the ICV and the idle will raise up again.

I had an idle-only misfire once on a 1986, it was due to the pipe going from cam cover to air cleaner coming loose.