1993 Ford Explorer Idle speed

My car is almost struggling to idle. It never dies...but the idle speed will go low to about 500 rpm's and then spike back up to 1000. I also have a check engine light. I had suspected the Idle Air Control valve to be bad but I'm not sure. Since it's not exactly cheap I didn't want to waste money on it if that's not the problem. I also tried to get my check engine light code with the turn on and off 3 time procedure but was unsuccesful...it never blinked. So here's my questions--With out using the computer diagnostic...since I can't find anywhere that has one for a 1993; how can I get my engine codes? And, What would be suspect to the problem I'm having?

Thanks