Broken exhaust manifold=blown valves

The story.

I was driving home from work when i hear a hiss dont think much of so i continue to drive, the hiss gets louder and louder, then the bad stuff happens. the check engine comes on and i know that i have issues that are getting worse but have to get it of the highway because its a toll road. a mile from my exit it gets real bad and start to slow down even with the pedal pushed to the floor (i know bad idea right) then cel starts to flash, and engine starts to shake. get it off tow it home and start diagnosing problem has only one code for random multiple cylinder misfire. so start with the obvious and went to plugs and wires, no go. then to coil pack, no go. then to vacuum leak, no go. then compression tested and guess what cylinder one and three are bad not getting over 90 PSI (tested multiple time). so did a wet compression test with the same results. removed the heads and put some sovent in the runners and they leaked like no other. so i started tearing down, i thought originally that i would just get the head redone and put them back on but then i thought, its down this far so why not hone the cylinders and rering the bottom end while im at it, now i am just waiting to put it back in, will post more pics as i get closer.

Any signs to what may have caused the problem??? :idontknow: Ive seen Catalytic converters that were plugged up (usually due to a missfire cause by an ignition problem) that have overheated and cracked an exhaust manifold and the back pressure burning out your exhaust and intake valves. Im just curious in what you may have found...thanks for keeping us posted!

So far the only thing I have found is the bad valves, the visual inspection of the cats that can be seen look ok, but that doesn't mean the second cat isn't bad, I would hope that the o2 sensors would throw a code if it was a cat that is one of their jobs. I will keep everyone posted when or if I find anything new

well now that i finaly have every thing back together the root cause of the problem was indeed bad catalytic converters, the drivers sid cats were bothe completly blocked it broke three rings and fried the valves, so every thing went back together good and she is running awesome right now hopfully it stays that way for a while.

Nice post and great pics! I have seen quite a few bad cats on JK's. Glad to hear you got your problem fixed :thumb:

glad to hear you're back up and running. did you do all the repair work yourself? Sounds like it could be expensive fix. How many miles on jeep?

Yes it is back up and running, along with the bad cats and burnt valves i also had three broken piston rings. Luckily the bad rings didn't do any damage to the cylinder walls. I did all the work myself, i honed the cylinders cleaned all the parts, pressure washed EVERYTHING, started reassembly. new rings, all gaskets, and everything that goes with an engine rebuild. this is my 32nd engine rebuild (started rebuilding when i was 14 now 30) i have seen some really bad stuff this was minor compared to some stuff i have done. All together the JK is running great i have got through the breaking and it is still running great. hope it will last a while. if not i might go with a 3.8 stroker kit and a supercharger.