My 97 Accord is idling funny after the car warms up. When I come to a stop at a red light, the idle will drop down to about 100/200 RPMs and the car feels like it is going to stall but has not stalled yet. It stays there for a second or two and then goes up to about 400/500 RPMs and does this cycle a few times before leveling off around 500 RPMs. Sometimes it never levels off and will continue to drop and rise the whole time I am idling. The a/c makes it worse. If the a/c is not on, it still does this but not nearly as often. If the a/c is on, it happens at every stop. I have already tried a tune up. (Plugs, wires, distributor, rotor, PCV, air filter). I also changed my oxygen sensor because my check engine light was on. Since I replaced the oxygen sensor, the check engine is no longer on. Any advice.