Catalytic Converter issue or something deeper?

[Dustin Gebhardt]

As Train said, some diagnostic work is now warranted. Move the COPs from the offending cylinder(s) and see if the issue follows the COPs. Th pigtail connectors on the COPs are also known to have issues. The rubber rings break and let moisture into the connector. And the plastic locking clip breaks, allowing the pigtail to come loose. You can also move the spark plugs from the offending cylinder(s) and see if the misfire follows the plug. Cylinder 4 and 5 are on different catalytic converter banks, FYI. What are your upstream and downstream O2 sensors reading. The upstream sensors should cycle up and down in voltage. The downstream sensor should mostly stay constant. If it bounces around, then the cat is likely bad. You can also check exhaust temperature at the exhaust manifold and at the front and rear of the cat. If the heat is abnormally high in front of the cat, then the cat might be plugged. You can also check the fuel injectors. Move the ones in Cyl 4 and 5 to a different cylinder and see if the misfire follows.

 

[ChrisRCNY]

I had a misfire that would appear when the engine got hot, and vanish when it cooled down.

Clip on the coil's input wire was broken, and the silicone the police dept mechanic slathered on everything made the seal work really well. Trapped air would expand, push the connector out, misfire a lot until it cooled and reseated.

Fix was to hold my finger on it long enough to leak down, no issues for 6 months now.

 

[Bob Sheets]

Cylinders 4,5 and 8 were misfiring.

Replaced the coils on all three but #8 still misfired. Pulled the plug and it had a hair line crack in the porcelain and basically fell apart when I pulled it out of the socket. Replaced that and everything is smooth.

Now, I have a P0430 bank 2. That's the left side of the engine,correct? And that's a converter,right?

 

[Trainmaster]

It means that the voltage the oxygen sensor is producing is out of its expected range. You should now find a code reader that can read the voltage coming from the sensor. It could be a bad oxygen sensor, a bad converter, bad wiring or an exhaust leak. Real-time charting of the voltage output, along with perhaps a digital thermometer should narrow down the cause.

On our engines, Bank 2 is the left (driver's) side.