i have a 98 accord, 2.3 l v-tec with 250 000 km. I have had a cil code p 0420 ( catalitic) for about 5 months. The car was running fine but I changed the front o2 sensor (cheap brand) about 2 months ago but that didnt clear the code. The last 2 weeks i stalled twice while going like 50 km / hour and i have intermitent problem, sometimes the car doesn't want to move at all while i am driving like 40 km/ hour or so i press the gas and the car just jerks but doesnt catch after about 10 secs or so it goes back to normal. I unplugged the o2 sensor in the front and that problem completly disapeared (its been 3 days since) Anyone know eaxctly what the problem could be? Bad cat, bad o2 sensor etc....
how can i fix this problem in the cheapest possible way?

 

tap on your cat when its cold and see if it rattles inside. if it does then its most likely bad, otherwise, its your o2 sensor.