Symptoms: Car has a long standing CEL. Ran the codes as random missfires for each cylinder and fuel too rich. Warmed up and sitting in neutral, everyone tells me the car sounds like its missing. If the car is up to temp and at a stop light, it runs slightly rough. When the fan kicks on, the idle goes bonkers and the CEL blinks. When the fan turns off or you take off from the light, the CEL goes back solid. Also, under various conditions if you blip the throttle in neutral the car will stumble and die.

Things I've checked: Today with the car running i pulled each injector plug starting from the firewall forward. As I pulled each one, the car stumbled accordingly until I got to the last one. I pulled it and the motor did not stumble at all but the CEL inside did start to blink (I'm pretty sure it had nothing to do with the symptom I described above, I verified this multiple times). Next, with the car in neutral I put a load on the motor up to about 4k with the injector plugged in and with it unplugged and there was a discernible difference. Motor was not eager to rev with the injector unplugged and sounded like it was straining.

From that test, it looks like that cylinder for whatever reason is not firing in a low rpm/idle condition. I had the same symptoms a few months ago and had the injector replaced with a known working injector so I can pretty much rule out the injector itself. That only leaves the spark plugs and the coil pack, both of which I'm going to attempt to check this afternoon after work. I'm also going to pull the the o2 and see how bad they are.

Any ideas of what else to check? I have a few hours before I head in there and I'd like to explore every possible option.