Q: Car rpm bounce at idle

Hi There, Your car has a small purge valve called a purge solenoid in the Evaporative Emissions system that controls the venting of fumes from the fuel tank as these fumes build up inside, particularly when you are refueling the car with gas. The EVAP system prevents fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system collects and temporarily stores the fuel vapors in the charcoal canister. The charcoal canister is filled with activated carbon pellets that can absorb the fuel vapors. When the engine is running, the fuel vapors are purged from the canister and burned in the engine. The vent control valve (solenoid) controls the flow of outside air in and out of the charcoal canister. The vent valve is controlled by the engine computer (PCM).

I think you are on the right track in terms of things to check. The RPM fluctuation is likely a result of the faulty purge valve. When there is a leak present in the EVAP system, this can cause the mass air flow sensor to read incorrectly causing the RPM fluctuation you describe. The code related to the O2 sensor being lean is also likely a result of the affect the problem described above relating to the mass air flow sensor due to an under fueling problem. I would suggest having an expert from YourMehcanic come to your location to take a look at your vehicle.