Idle Seems To Rich

97 DX, 5 spd, 1.6 non-vtec engine. Ok, been having idle problems lately. Rough idle and low idle at times, irratic and only occasionally. Mechanic friend said clean out throttle body, could be coked up with carbon. It was, so I did. Now idles great and runs great through all RPM's, but seems to idle excessively rich. My question is, can Idle air control solenoid malfunction cause rich idle? The idle is perfectly steady but seems overly rich. Has strong smell of gas vapors in exhaust while idling, not normal smell I'm used to from this car. No check engine light, but haven't checked for codes yet. IAC solenoid messed up? What do you think? MAP sensor? Air charge temp sensor?