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?

Learned something new yesterday. Fuel injectors that stick open a little longer than they should can cause rich running condition. When I start the car on cold morning I would hear a 1/2 second of tapping from the engine somewhere, then it would go away. I thought maybe it was a valve, but now I'm wondering if it wasn't a sticky injector. I put some injector cleaner in the tank and got fresh fuel. Hopefully that helps.