my 2007 jeep wrangler 3.8L i am showing 2 codes po300 and po420 please help me

Question

2007 3.8L jeep wrangler i have to codes  po300 and po420 the jeep runs real bad backfireing

Answer 1

Hi there,

This is one of those funny ones where the P0300 multiple misfire code could actually be causing the P0420 catalytic converter code. I would start by pulling the front O2 sensor from the exhaust before the converter on bank 1 and see if it runs better. If it does, then the converter is likely plugged, if not then you know the exhaust is fine and you can look for the misfire on the engine. Check for low fuel pressure, a tune up, possibly intake manifold leaks, even the engine timing could be off. Ignition coils could be the problem as well.