Hate to hi-jack a thread...but it is related.
In regards to:
How do you check a cat? I've been told to hit and it will sound like marbles if it's bad. So, can it still be clogged and not sound like marbles?

Then I was told to get a thermal camera (right, like I have one laying around) and check the inbound/outbound ends of the cat and see if the temps match. It would just be cheaper to replace it the cat than mess with the camera.

So that was my response...then I was told the cat is designed to last the ENTIRE life of the vehicle. That sparked another debate. Anyone have some concrete data for me?

As I stated BEFORE:

If you smell rotton eggs when your car is running then thats a sign the cats plugged.

Did I once imply to go and buy a thermal camera and use it to check your cat? If it was plugged bad enough it would make the exhaust glow orange and you dont need a thermal camera to see that.

It should definitely improve after that repair.

The "life" of the vehicle doesnt mean it'll never last. It means it will last for the time the average person owns it. Basically any Cherokee could have a bad Cat now.

Ive run injector cleaner and sea foamed it. I also think theres a problem with it but ive yet to find it. New o2 sensor, tps sensor, plugs and not using ac i only get about 11-13mpg. Also has new fluids and air filter. No codes or check engine light either. I sometimes smell gas when driving but there are no gas leaks.

If you can smell the gas then you are either running too rich or you have a small leak somewhere, on mine it has a small leak down where the mechanical fuel pump connects to the hardline, it doesn't leak enough to drip but it keeps the fittings wet and you can constantly smell the gas, but I have a carb on a 2.8, so you would have to check all the fittings back to the fuel tank and smell the exhaust to see if it is burning rich.

if "improving" was spelled right, I would care to post a positive comment in this thread.

poor spelling skills suck.

wait, we're improving gas milegeage in this thread? i thought we were imporving it, oh im so confused! . Really, don't be so nit-picky about it, you sound like my English professor.

Injector O-rings?

I was thinking about replacing the injectors and ignition parts but will be disappointed if there is no improvement and I wasted that money.

what year is your cherokee?

Another thing, check your plugs and wires, and the contacts on your distributor if its a 99 or prior. That was giving me some bad gas millage for awhile because the contacts on my distributor were shot, along with my plug wires.

i don't think thats entirely accurate, even my 89 renix doesn't have a points distributor, did you mean the cap and rotor?

Sorry, i was refering to the contacts and got the two confused. Dont multi task and post lol

No, I was merely stating that I've been instructed to do this elsewhere.

Well that just seems like a waste personally. If your cat was plugged youd know it, i dont think youd need something that exspensive to tell you that its plugged.