My 2000 Verada is running LPG and is half a million Kay's old.

My idle tends to sit at about 500 rpm and stalls a reasonable amount when running on gas, less so on petrol.
I pulled the ICS out and cleaned it, which seemed to reduce the stalling, but it's beck again.

The stalling only really happens when slowing down and the trans (it's auto) tries to downshift and I loose the engine braking effect. It's worst pulling off the freeway slowing from 100 to 80 to take the off ramp, the extra load from the PS kills it. At the moment I manually shift down and give a blip on the throttle to get around this.

The idle speed is basically the same in gear or not, but I suspect that the trans isn't really in gear at such low revs, due to the trans pump not working properly at that low RPM.

How can I test if my ICS is working? I don't want to go replacing the thing if it's not the problem.
Got a multi meter round here someplace, can someone give me a pin out and voltage ranges to check it's getting signal please?

I was considering testing by throwing 12v at it, but to many wires and a nagging thought in the back of my head that I'll fry it doing that.

Help!

The ISC contains a stepper motor so just attaching 12V across one of the windings isn't going to achieve much. Somewhere I've read that you can check the resistance of the windings (there are 2 phases) - I suggest a search in the W/S manual for the specs. However, have you also cleaned the throttle body? If the air bypass ports that the ISC regulates are gunked up the effect can be similar to a failed ISC.

I emptied half a can of carbie cleaner into every orifice I could find that looked remotely connected with the ICS, but I forgot to actually open the throttle body! D'Oh!
Might give that a crack tomorrow and see how it goes.
The ICS was fairly clean though, so I don't hold much hope.

Got a PDF of the manual the other day, so I'll have a paroose through that.

ISC doesn't work on 12 volts, it works off a pulsed signal from the ECU at a lot less than 12 volts.

Pull plug, you will see 2 rows of 3 contacts.
Measure resistance from the outside of one row to the middle, compare all 4 readings. If one is open circuit, the ISC is toast.

Update.
I re-washed all the ports for the ICS because I forgot to open the throttle body. When i put it all back together I forgot to plug in the ICS. It made zero difference to my idle - fair bet either the ICS is toast, or my wiring is U/S.
Kids stole the battery and leads out of my multi meter - so going to get another cheapie in the next couple of weeks and test properly.

the two center pins of the ISC connector should be +12v
when checking the coil resistances the standard value is 30 ohms +/-3 ohms
other tests are to listen for the isc when you first turn on the ignition when the engine is cold.
also bucking the steering wheel when the engine is at a stable (and warm) idle should result in the tacho immediately rising (as opposed to dipping then rising).

my ISC recently crapped itself and whilst it checked out electrically, the front seal on the shaft was leaking, as was the internal seal so it was filling with dirt and oil, then clogging up. i found that out by removing then opening up the motor (2 screws). a clean out only resulted in about a month of trouble free operation.

i got my replacement from here (www.ebay.com.au/itm/New-Genuine-Mitsubishi-Magna-TH-TJ-3-5L-Oxygen-Sensor-Idle-Speed-Control-Valve-/121084185863?pt=AU_Car_Parts_Accessories&hash=item1c312e0d07&_uhb=1)..... a lot cheaper than trade price in perth (250 after market or 400 genuine just for the isc)