Now have a P0303 code...
 

I have a 2005 MPV...My light came on a few months ago, it wound up being I needed a new catalytic converter (left bank2). First the mechanic tried doing a tune-up, thinking that it would solve my problem, that didn't work...still miss fired. So I got the cat. conv. replaced. A couple of days after it was replaced, it started missing again, the light just came on yesterday (it has flashed a few times today). Took it to Autozone and it came up with a code of P0303. What is the next step I should take?

A P0303 code means that the the car's computer has detected that one of the engine's
 

A P0303 code means that the the car's computer has detected that one of the engine's.
Symptoms


Symptoms may include:

• the engine may be harder to start
• the engine may stumble / stumble, and/or hesitate
• other symptoms may also be present

Causes


A code P0303 may mean that one or more of the following has happened:

• Faulty spark plug or wire
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector
• Burned exhaust valve
• Faulty catalytic converter(s)
• Running out of fuel
• Poor compression
• Defective computer

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.