88 Xj need help

picked up an 88 xj with a manifold leak, and a power steering leak. Replaced the exhaust manifold and the power steering pump.
The Jeep starts and idles ok for about 1 min then starts acting up as it gets hot. It starts running worse and worse as the themp increases.
The CAT on it raddles very badly
Was wondering if this would cause the engine to run this bad
Thanks
Brad and John

plugged CAT? try straight pipe

if your CAT is plugged, you're going to have too much backpressure...creating too much heat...especially in your headers/exhaust manifold....leading to cracking....

Not sure if a straight pipe would work for you - doesn't CO have emissions testing?

i ment just to try out. i live in michigan, the land of, "we don't care"

NM is the same way, but I think CO is up there with CA as far as emissions testing....LOL....

when you say the CAT rattles, you mean if you bang on it with your fist, you can hear stuff rattling around like, oh, perhaps some broked up pieces of ceramic....? if so, take a saws-all and just cut your cat out, do what 74charger said and get a piece of straight pipe to slide in there, and see how it runs.

boomer1 said:

picked up an 88 xj with a manifold leak, and a power steering leak. Replaced the exhaust manifold and the power steering pump.
The Jeep starts and idles ok for about 1 min then starts acting up as it gets hot. It starts running worse and worse as the themp increases.
The CAT on it raddles very badly
Was wondering if this would cause the engine to run this bad
Thanks
Brad and John

Click to expand...

Just replace the Cat. If it rattles it has come loose or come apart and is causing a restriction that will only get worse, Also check the muffler for pieces of the cat that might have made it to the muffler which can restrict the muffler as well.

While the engine is running, the cat is rattling really bad. If I put on a glove and put my hand on the cat, you can actually feel something inside, banging around. I know the cat is gone, so I plan on replacing it. YES, Colorado is strict about emissions. Like I said, it starts up and runs, then it's like the computer is trying to compensate for something. The idle runs up, then drops, then up. Actually starts backfireing through the intake, in the air box. Hoping that the cat is causing it. Replaced a broken exhaust, put new plugs, rotor, cap, wires and still does it. Everything looked pretty old, but it did stop the problem.
Thanks

Oh, also replaced the O2 sensor. Figured with the crack right above it, it was also shot.

If your CAT is rattling, it's shot. Take it to a muffler shop and replace it and like said above have them check the muffler too. Air out is just as important to running as air in, if not more so. I replaced my CAT and muffler with Magnflow's and the Jeep runs like greased lightening. Sent the smog police packing too.

That bad cat is definately the major cause of all your problems, been there done that more than once! If you still have the same problems after replacing the cat, then part of the cat guts are in the muffler blocking it as well, if that is the case replace the muffler second.