accord with issues

my car seems to act as if it is cutting off when sitting idle or just driving, i chnaged the main fuel relay, spark plugs and it still acts like it is going to cut off, i can be driving downthe road at speeds of 55- 85 and it will give a little cut back, at times it is worse that others ...also when i turn on the ac it almost totally dies, and one day sitting at a light with the air on it cut completely off...nto sure what the problem is ...please help..need soon, going on road trip in 1 week:confused: