First you have to know the exact fault code number. There are about a dozen related to the idle air control valve, and they mean very different things. That system doesn't have anything to do with the evaporative emissions system. Also, that system, which is also referred to as the "vapor recovery" system, isn't monitored on '95 and older models, so while it could have a leak, that won't be detected by the Engine Computer and it won't set a fault code.
To find a leak in the vapor recovery system, you really need a smoke machine. That allows you to inject a white, non-toxic smoke at 2 pounds of pressure, then you can watch for where it sneaks out. Other than that you're limited to a visual inspection, and that is only good for real obvious problems. Most leaks in this system are way too small to see by eye.
For the idle air control valve circuit, I already mentioned checking for bare wires and corroded connector terminals. Beyond that the testing gets a little more involved. You can use an ohm meter to test the resistance of the wires and the motor that runs the idle air control valve, and I mentioned the scanner for running the motor through its paces to see if it responds properly. There really isn't anything you can do yourself when a scanner is required.
Saturday, April 4th, 2015 AT 8:17 PM