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Hi, I have a Civic LX (engine D16Y7) that's been misfiring for a while now. I've tried numerous things to try to solve it, but so far I've come up empty handed. Lemme give a run down of what I've done so far: I've put brand new spark plugs, spark plug wires, cap and rotor, distributor, alternator, fuel filter, the battery has been tested a few times and is good. It has never had trouble starting, it has never died from a misfire, and it usually idles fine. it only idles rough and low after it has been running for a while and is hot. it misses consistently when the engine is cold and I start it out at a low rpm and push the gas hard and it goes from a hard take off to slowly decelerating for a few seconds and then kicks back in and goes. once it warms up the misfire becomes more like a hiccup than a pause which this I thought would be a problem with the fuel system. However I discovered one day that while the engine was hot (running temp, not overheating) and idling, it would idle solidly at 800-900 without fluctuation, but when I press the brake pedal, the instant my brake lights come on the idle drops to about 500 and gets rough. it does this whenever I change something electrically (eg. headlights on and off, radio on and off, most dramatically with the brake lights). I've put oil treatments in it to clean gunk off the valves, fuel treatments to clean the injectors, I've listened to the injectors (all are functioning properly). I've tested the throttle position sensor, the MAP sensor, the fuel injector resistance, all the grounds that I could locate (with help from the Hayne's manual). The only discrepancy I've found is the O2 sensor heater circuit is not getting voltage on the negative wire. other than that the sensor is fine. the only CEL codes I've gotten were random misfire, cylinder 1 and 2 misfire, and cat system operating below efficiency. And I can go almost 2 months from resetting the CEL to the same code coming back. I have had compression tested also, and it is good. The timing is off a little, but not bad, so would a combination of the O2 sensor and bad timing make it misfire that bad? If anyone can help, it would be greatly appreciated; I'm kind of grasping at straws at this point. Thanks