Gross Poluter

My 2001 Toyota Celica GT was put through a smog test and it was running rich on the idle only. It has been tagged a gross poluter and so i finally got a code reader to try to diagnose why. When i plugged in the code reader it kept stating no codes. It does not have a check engine light on and has not had a tune up for a while now. I am in real need of my car now more than ever. Please provide any help whatsoever.

it probably needs a complete tune up including stuff like plugs, wires and distributor cap (if it has them) air cleaner, pcv valve and maybe some injector cleaner. can't hurt

It may be your coolant temperature sensor.