P0303 code - catalytic converter?

[phasty20]

Hello,
I have owned by TJ for about 2 months now. It's my first Wrangler and I love this thing. Most importantly, my wife and daughter enjoy it as well.

I recently had a P0303 misfire code. My first step was to install new plugs. I replaced the Champion RC12ECC's with Autolite XP985's, cleared the code, and it later came back.

I noticed the driveshaft tunnel gets hot on longer trips. Being my first Wrangler, I just assumed it was the way these vehicles are due to lack of insulation. But we are talking "hot" as in my Yeti cup gets so hot it's uncomfortable to hold after sitting in the cupholder for a long road trip. This leads me to believe there is a clogged catalytic converter. I just got a laser thermometer and will test this weekend. Is it likely that a clogged converter could cause the misfire? All the plugs looked PERFECT and fairly new. I'm thinking the previous owner may have had the same code and replaced the plugs in attempt to fix it.

 

[Chris]

Have you visually inspected the cats after driving for a long period of time? Often times when they are clogged they will glow red.

It sure sounds like clogged cats to me though. The transmission tunnel does get hot, but the way you are describing it is hotter than any of mine have ever been.

Usually clogged cats will also lead to a loss of power.

 

[phasty20]

I checked the inlet side and outlet side of each cat today. After about 40 minutes of driving, each read within a 10 degrees of each other. The hottest reading I got was 590 degrees. No check engine light either. If it were a clogged cat, I wouldn't think it would be an issue that comes and goes. I'll keep an eye on this issue and report back.