Hey everyone got a 01 corolla with 291,000 on the body and about 150,000 on the engine. I am having some major idling problems. sometimes I can start the car and it will do ok. Other times the rpm will go to about 1800 then drop well below 1000 until it bogs out. When I put it in drive the immediate acceleration is very erratic. Almost like the engine is choking. I am also getting very poor gas mileage. I have had my mechanic work on it and he replaced the tips and it helped some but not much. The only code that is coming up is p0420 which is the catalytic converter. Would that cause my problems? Any ideas are welcome this is my vehicle I commute to work with so I need it running soon. Thanks