Subject: 91 Galant Idle
Question:

I Have a 91 Mitsubishi Galant ls A/T 2.0L
The engine is idling rough and it smokes the smell is of too much fuel. I replaced the the Oxygen sensor.and still the same problem.I replaced the plugs wires and cap and rotor but still the same problem.
I then checked the IAC and I noticed that it is not touching the throttle plate and it is going in and out I tested the motor and the motor is working fine but the sensor next to it might be bad I will change it. my question is will this sensor cause the engine to run rich I know that all the sensors will work collectively. I have checked the injectors and the ohm reading is 15.1 to 15.3 on all four and they are getting voltage to all of them. 
Answer: Mike,
A faulty idle or intake sensor may cause your problem. But since all your sensors are tied together by your car's computer, I'd recommend checking that as well. Read this article for further information:
http://90gsx.com/eclipse/cap/caps.htm

If your ECU is malfunctioning, you'll notice all sorts of odd problems. But it's always good to check all your sensors individually to be sure they are functioning correctly. Rough idle can also be cause by a worn timing belt. If it's been 60,000 miles or more since your last belt change, it's a good time to change timing belt.
Good luck!