Mitsubishi Repair: 94 Lancer executive, kinds of sensors, injector cleaner

Question
I have recently purchased a 94 lancer executive, auto trans(which was replaced about 6 months/ 20000kms before I purchased the car), and the car idles really low (under 1000rpm, about 200-450rpm) when the car is in drive but not moving, eg at the traffic lights. I have had a tuneup, replaced the spark-plugs, put through the injector cleaner, and have started to use a higher octane petrol, but it hasn't helped the problem. Do you have any suggestions as to what I can try next? Could it be an emissions sensor? or something to do with the cats?

Answer
Alana: I would have the car coded, as it sounds like a computer or sensor problem to me. There are all kinds of sensors in your car's engine, even back in 1994 model. Find a shop and tell them you want to have your car coded, they will hook your car's computer up to their computer to see what is kicked out. Mitsubishi had some problems with bad computers because they have another company build their computers. A piece will start to leak into the computer and with time it kills off the computer. One way that shows up with just with what your car is doing. But there are sensors are that control that idle too. So have it coded and see what that tells you. Cats? God bless! Linda