A couple weeks ago my CEL came on (misfire cylinder #8) my first thought was plenum, so you don't have to reply with a link to the thread. I checked my spark plugs and they were all bad didn't look like they were ever changed. So I changed them and it ran fine, didn't get the CEL again.
This past weekend I was driving and I could hear the engine misfiring on a hill and the CEL came on again, I let off the gas and made it up the hill, got to the top and just cruised down, the light went off, and didn't come back on. No code came up when I checked later.
So I'm planning on selling the truck soon so I don't want to start digging into the plenum, but I think I have to replace my cat. Just want to make sure before I order one. I have to do this quick because I need to go somewhere on Sat. about a 3 hour round trip. And I need to take my truck.

 

Why replace it? Why not cut it out (salvage it cause they fetch a decent price) and by pass it?

Does your locality require emissions testing?

 

I was thinking that, their not doing emissions now, but I was thinking it would be eisier to sell with one. I was thinking a magnaflow universal one, less then $100.
If I just bypass it, won't I throw a O2 sensor code?

 

I think I'm just going to go with the magnaflow, might sound stupid but what one do I need, inlet and outlet size?

 

The one i got was two 2" inlets and one 2.5" outlet

 

I just went out and looked, I thought the cat had one o2 before the cat and one after, mine has one going into the cat. and is there any way to measure the pipes without cutting it?

 

Yeh there is an o2 sensor in the cat on the front of it and the universal magnaflow has the same spot for the sensor and the o2 sensor screws perfectly into the new cat. You should have the same exhaust set up as i do, here is the diagram under the FAQ section on here:

 

Ok thanks. I've seen that diagram before. I always completely forget to go check the FAQ section.

 

No problem!

 

Cyl 8 misfire can be caused by spark plug wire routing.