Cincidsm - FAQ

Idle Speed Control (ISC) Test/fix page

Let's talk about symptoms:

When you are coming to a stop and push the clutch in and let off the gas does your Idle Drop Below 750 and almost stall (or stall)?
When you turn on your A/C does your car "Idle up" or does it go down?
Just a general Bad Idle? (not missing but just bad control of the Idle)
If you are having an Idle surge problem and the below steps find that the ISC is Good, please check out Terry's Troubleshooting page on Idle Surge

If you have any of the above symptoms you MAY have a Bad ISC. I am going to show you where it is (ISC) and how to test it. You will only need your hands and a Multimeter to test it.

The ISC is located underneath the Throttle Body, on the back side.

Testing this thing!This is a pretty simple process:

Remove the connector to the ISC

There are six pins on the ISC. They are labeled 1 2 3 across the top and 4 5 6 across the bottom. (see left)

Measure the Resistance between pin's 1-2, 2-3, 4-5, and 5-6
Each pair of pins measured should read 28-33 Ohms
Note: The values should measured with the car off and cool!
If any of the "coils" (which is what you're testing) are bad then your ISC needs to be replaced
If all the coils were good there's one other thing to check on the ISC
Use a 6volt battery (lantern or camera battery) and apply 6 volts to the ISC motor.
Use jumper wires to connect the positive (+) terminal of the battery to terminals 2 and 5 of the ISC and the negative battery terminal to terminals 3 and 6 of the ISC.
If there is no movement or vibration from the motor, then it is bad
Note: The use of a 12volt battery will destroy the ISC motor!!

Now that you know that your ISC is bad, you need to find one! Start calling around at the local junk yards. The ISC for the 2.0L engines are all the same for Turbo or Non-Turbo cars. I have a 92AWD and I'm using an ISC off of a 93 Non-turbo and it's working great!

This is a very simple task...

There are two screws that hold your ISC on (an 8mm socket works great)
Remove the screws and pull it off
Be careful, there's a little rubber O-ring that can fall out

This I'm not sure about yet. I had to break the plastic on my old one to get it apart because of a screw that wouldn't come out! I could have drilled it out but it was broken already so I wasn't too worried about it. Here's what I found, inside there are quite a few pieces, two of which seem to be the problem with these things. There are two coils inside which are soldered to the pins on the outer (brown plastic) piece. Each coil actually contains two individual windings. When looking at the coil it's covered in plastic and has three connections on it. The one on the left to the center should read around 25-30 Ohms and the same goes for the center to the right. I think if I could have gotten the plastic off without breaking it I could have replaced the bad coil (this is assuming I could have found a donor ISC to remove a good coil from). Now If I can find a broken (half broken that is) ISC I will try to repair it with my one good coil out of my original ISC. Will this work? I don't know, but if it does I'll post it you can bet!