Flooding problem '90 Camry

Need some help with my daughters 1990 Camry 2L 4 cyl. This car has been very dependable over the years. Every once and a while it would start giving her problems with stalling and hard starting and I found the problem was always with the distributor cap. The metal posts the rotor spins past would grow deposits that I could scrape off and everything would be good for a while. It would really be bad in wet weather. Sooner or later I'd have to replace the cap after those posts would deteriorate away enough and she would be trouble free for a good year. Then eventually the process would start all over again. But now it must be something else. The other night I happened to be outside when she started her car cold (it was around 15 degrees outside) and it started very rich. The engine ran like the good old days of stuck chokes. Chug, chug, chug with very black smoke out of the exhaust. This went on for a good minute then she let off the gas and it died. She managed to get it started again and it then ran just fine. She then proceeded to say, "this always happens". About a week earlier than this it would not start. I was not aware of the rich fuel problem but was able to diagnose she flooded it. I removed all the spark plugs and dried them off. It then started immediately after that. But it did chug out some black smoke before it ran smooth. So bottom line, it is flooding out intermittently and unpredictably. Any suggestions? Is this a fuel delivery problem or an ignition problem. I read in a different thread that weak ignition can cause the engine to basically flood if the spark does not get the fuel burning fast enough. :banghead:
Oh yeah, and the check engine light does go on sometimes during this process.

Update...

After reading a bit more about oxygen sensors and what can trip them up I went back to the Camry Monday night. Had to do the brakes and brake light switch anyway. She was also missing a stud for mounting the exhaust to the manifold so there was a small leak there. One of the things I read that can screw up an ox sensor is if there is an exhaust leak close the the vacinity of the sensor. It can get a false reading of too much oxygen under certain conditions especially if the leak is where the manifold mounts to the block. This leak was down wind of the sensor but it was within about 4" of it. So I replaced the stud and tightened all 3, the leak was gone. I also pulled the ox sensor and cleaned it off with a fine wire brush and blew it out. That was Monday. My daughter called us today (Thursday) and said the thing is running like new. Before this it was easily stalling 3 to 4 times per day and sometimes flooding so bad it would not restart. So the fix cost her about $3.70 for the stud and nut. Thought I'd let all you readers know what worked for us. Still plan to replace the censor with a new one.