Ladies, Gentlemen, and Children of ALL ages, do I have a treat for you. My 2000 Disco is definitely not purring, in fact it's running like total A$$. It is running very rough, at idle seems to be at half power during acceleration, and it also seems to be leaking exhaust around the seams of both cats. Check engine light is on showing the following codes:
P0304 cylinder 4 misfire
P0302 cylinder 2 misfire
P1300 no idea what that is
P1884 multiple definitions
P0300 random misfire

I am leaning toward replacing the cats and O2 sensors, just wanted the opinions of this esteemed crowd first. Thanks any help is much appreciated!!

 

cats and O2 sensors would not be the first place I would look, neither one will cause a misfire.
"I" would look for an ignition problem (plugs wires) and whenever I see multiple misfires side by side I have to ask How's your coolant level?

 

Coolant level is good, oil tests were all clear. I run Chevron 10/30 Supreme in spring/summer and chevron 5/30 Supreme in fall/winter, with Baldwin filters all around. Due to my profession I have access to free fluid sample testing and test oil every 3000 mi. The exhaust leak at the cats and (did I mention?) the weak/sputtering exhaust at the tailpipe had me leaning toward the cats.
I thought that I had read that an O2 sensor reading not enough fuel, due to a clogged cat, could cause the ECM to dump more fuel into the cylinder and therefore cause a misfire due to a cylinder being too wet? Maybe I misread that.
Do you know if there is a way to test a coil while it's off, so that I don't have to just throw parts at this and then tear down and build up the intake over and over again. I figure that cant be good for the upper intake gasket. Mind you I could use new valve cover gaskets, so this could be a great excuse!

 

i would start by moving the wires and plugs and see if the faults follow

 

I will. Thanks!

 

This is from an absolute unqualified position, but it's where my mind went immediately: any chance something is just blocking your exhaust somewhere after the cats? Like something crawled up there to die (hate to say it, but like the furry kind).

 

Checked the plugs and wires last night, did it at night so that I could just remove the spark plug reattach the plug wire and start the truck to tell if there was spark. Everything firing the way it should. And no, I hadn't entertained the thought of something furry crawling into my exhaust and dying. But, you never know.

 

I figured, screw it and replaced both cats with universals. After a little exhaust tubing fabrication I got the both to fit very well. Cleared my codes and after 3 days of driving no more codes!! Thanks to everyone for your help!!

 

Glad to hear it is running well but what clogged them in the first place? Usually that is due to them overheating and melting from running lean or they get fouled from the truck running too rich. Just hate to see them get trashed again. By the way, many D2 cats bring good money when recycled so make sure you take them to a decent scrap yard. Might get a enough money to cover the next repair! Oh and regarding the unknown code a P1300 is Catalyst damaging level of misfire on more than one cylinder.