bad cat or engine / sensors ?????? 4.0

[dogkatcher]

alright ... lowdown on jeep: bought it 108k (no history) .. now has 124k .. bought it in may 07

cherokee laredo 4.0 4x4 manual

- new plugs & wires, fuel pump just after bought .. also cat / muffler (from a cheapo shop)... new crank pulley also . replaced h2o pump last winter

recently have had problems with hesitations gettin on highway in morning .. backfired twice in a months time, backfired after a pause .. sometimes hesitation will happen just ridng at 2k rpms for a while .. colder weather seems to make it worse .. esp.. with high humidity

it is getting fuel.

- Just changed fuel filter, dist cap, rotor cap, new O2 sensor & checked plugs (all look great)

heres the idea: the was "new" muffler now sounds like a marraca, not sure about cat .. but since the O2 sensor looked really worn & that the exhaust will drip water when 1st started makes me think the cat is now clogged since deteriorated .. or gets frozen when cold .. maybe the whole exhaust is rotted/rusted out already & getting plugged up?

,,, the IAC is fine .. the TPS seems ok .... just cleaned throttle body.

any other ideas?? it will idle fine but when its on the road sometimes will randomly have "no power" but is still running .. then kicks in a she's off .. or will drop power & maybe stall out

why would a plugged cat cause it to pause ?? then stall sometimes

[fredjacksonsan]

What year is it?

A plugged cat will cause some of your issues, and I'd suspect that since you said it's rattling.

But also, some of your symptoms could come from a bad Crankshaft Position Sensor. Do a search under that and CPS and see if they match. The CPS usually lasts about 90-100k before quitting.

But since the cat's rattling I'd do that first.

[hundahunta]

I would check compression

[gtmud]

Get a back pressure gauge, You remove the o2 closest to the front of the cat and install. Start the engine, it should read 0. It sounds though like your exhaust is restricted, but I would verify before you go buying parts you may or may not need.