When checking ISC.
TR 4 cylinder. When at normal operating temp in park idle 1100 rpm. If I put air con on rpm will slowly drop to 900. Still in Park.
When in park idle at 1100 rpm, if I put it in Drive rpm drops too 750.
When in park 1100rpm if turn on air and put in Drive rpm drops too about 600=650.
Does this say that the ISC is not working????????

I know that my fast idle control valve is not working as cold start is 2000rpm in park.

Thanks to all that view and reply.

search - lots of threads on this topic.

I have searched heaps ,but still not real sure. My commodore the idle does not move. it is set at about700rpm in park it stays the same in drive with air con on.

I have read lots of threads but not to manny just have a clear cut answer. Should the magna be the same idle the same in park as drive???????????????

I know on the V6 it idles about 750 (manual) and when I put the air on it rises to about 850, not too sure what the auto is like but I would guess the idle should rise when the a/c is on

Base hot idle should be 750-850, cold start anything up to 2,000 rpm. Idle speed should be stable with lights on/off, in park or drive, aircon should pick up about 200 rpm. Sounds like you need a new ISC.

When checking ISC.
TR 4 cylinder. When at normal operating temp in park idle 1100 rpm. If I put air con on rpm will slowly drop to 900. Still in Park.
When in park idle at 1100 rpm, if I put it in Drive rpm drops too 750.
When in park 1100rpm if turn on air and put in Drive rpm drops too about 600=650.
Does this say that the ISC is not working????????

I know that my fast idle control valve is not working as cold start is 2000rpm in park.

Thanks to all that view and reply.

+1 likely ISC is not working.

1100RPM is certainly high, by what you're describing it does not seem like the ISC is good which is probably why the base idle has been set at 1100. Essentially your idle would be at the base idle speed regardless of what is on or in gear, that's the whole idea of it to compensate for additional loads.
The power steer pump has a load sensor as well so if you turn the wheel just enough to load the system up the idle should also raise slightly.
This may be a way of seeing if the ISC is reacting or I'm sure the manuals show you how to measure the coil resistance.

Hi , I used to work at a Mitsubishi dealership back in the 90's. I used to check the ISC by checking the resistance of the coils. I can't remember the exact specs, but there is 2 rows of 3 pins at the connector. Check that the middle pin of both of the 2 rows has the same resistance with the pin on either side of it.

Hi , I used to work at a Mitsubishi dealership back in the 90's. I used to check the ISC by checking the resistance of the coils. I can't remember the exact specs, but there is 2 rows of 3 pins at the connector. Check that the middle pin of both of the 2 rows has the same resistance with the pin on either side of it.

Yep, correct way of checking. Usually one side goes open circuit, and then the ISC winds in (or out) all the way and stays there. People compensate by winding up the screw, and then complain about fluctuating RPM. Another ISC is the only way to fix it.

Hi all,
Ok I went to the wreckers and got 2 isc. The first one I put in was exactly the same as the old one. I put the second one in and the revs shot up,,, OK I adjusted the screw with the little rubber boot covering it so that the revs came down too about 900rpm. If I put the car in drive it comes down to about 700rpm.
If I have it in park and turn on the air con the revs rise by about 200rpm.
BUT if I puy it in drive with the air on it dives down to about 500rpm. Is it a case of that I need to drive it for a day or 2 and it will adjust OR am I wasting my time and need to put another one in.
I will try the resistance test on the other 2 I have.
I,m starting to get a bit worried that it might be some thing else.

Sounds like its trying to do the right thing. Give it some time to settle.The second gen ISC is a bit slow at keeping the revs steady, the ECU isn't very smart or speedy. lol later Mitsus are much better.

Hi all again does any one think that it might be possible that the o'ring has a slight air leak???
The reason that I ask this is because if the car is in Park and you turn on the air the revs pick up and after about 10 seconds the revs start to slide back down.
Thanks for evey ones input

Hi , I used to work at a Mitsubishi dealership back in the 90's. I used to check the ISC by checking the resistance of the coils. I can't remember the exact specs, but there is 2 rows of 3 pins at the connector. Check that the middle pin of both of the 2 rows has the same resistance with the pin on either side of it.

Thanks for that one as that will come in handy when picking one at the wreckers,,,But the other problem is I think that sometimes the piston in side the unit also stuffs up. As the first one I pulled out tested fine with the multi-meter

Hi all again does any one think that it might be possible that the o'ring has a slight air leak???
The reason that I ask this is because if the car is in Park and you turn on the air the revs pick up and after about 10 seconds the revs start to slide back down.
Thanks for evey ones input


That's normal behaviour.