By air flow meter, I'm pretty sure you're talking about your MAF. I'm pretty sure it's right before your throttle body on a stock Rio. I'm nearly certain that your car will not run without it, unless you are running a stand-alone fuel management utilizing a MAP (manifold absolute pressure) sensor. A MAP sensor is in essence a boost meter. It senses how much load your car is under by the amount of pressure that there is on your intake manifold. Your MAF just senses how much air is flowing into your engine. The shop I took my car to told my dad that my MAF was bad and that was what caused my check engine light to come on. I didn't think it was true since my car ran, but my day went and shelled out like $300 for one anyway. Hope this helps!