89 acura legend v6 running rough

My acura (115k miles) just started running rough. It was running smooth
until about a month ago. Then it just started running rough. Now when i
try to crank it up, it takes about 5 tries, each time it only runs
about 1 second and then it dies. After I get it running, I can't even
touch the gas pedal or it will stall. I have to wait about 5 minutes
for it to warm up, even then, when i try to drive it off i can't give
it too much gas or it will stall..it takes about 15 minutes for it to
completly warm up. The exhaust isn't smoking or black, but it does
smell like the oxygen/fuel isn't mixing together very well, I can't
tell if it's lean or rich. I bought an O2 sensor, and i'm planning on
replacing that..but i'm not sure exactly what the problem is. Anyone
had a similar problem?