Will a clogged catalytic converter cause backfire? I have changed the fuel pump, alternator, spark plugs and wires, distributor, and rotor. My car still backfires with good fuel and air supply. I had a big cold air intake filter that deteriorated and the filament was sucked into the air intake. I am thinking it might have partially clogged my catalytic converter. The exhaust pressure is good I guess, I am just running out of reasons for the backfire. It idles fine and at anything under half throttle it runs quite normal. After half throttle though it bogs down and will backfire most of the time. Please help me.