New here...hello

My XJ isnt running proper...I've gotten a few mixed opinions and I'm jsut looking for more. I've done alot of research on thsi but there are so many possibilities I dont know where to start.

1992, 4.0, 150k miles

Symptoms...about 7 or 8 months ago my cat started rattling whenever I started the truck cold, went away after warming up (sign that its going bad). Over time the rattling went away but I started having rough starts...that would again go away once it warms up. Rough start meaning...the motor almost sounds and feels like one of the cylidners isnt firing. Until the engine settles down and runs normal I can hear my air filter "screeching" would be the best way to describe it

It still has the same rough starts and I am now experiencing a severe loss of power...can't drive it much faster than 30 or 40 mph even if I floor it...and if I do floor it I'll get a burning rubber smell and its not the tires.
The engine itself is not overheating however my under hood tempature is wicked hot...every peice off metal is getting hot enough to literally burn me if I run it for a while.
Oil is also getting spit back up the dipstick...however nothing is in the oil pan other than oil and there isnt too much oil in it

My best guess is the cat since thats where the first symptom began...I've also heard fuel pump/regulator or head gasket. I've also heard vacuum leak could be the problem.

Other notes...I've replaced the radiator, plugs, wires, cap, rotor, and fuel filter all in the past year.

Any suggestions on what I should be testing or looking for?

x2 on the cat converter, when it gets clogged its not alowing the engine to flow properly.. emission and such become backed up. While your changing out the cat i would also look into o2 sensors..That could also casue your rough ideal.. That would be the first step...

x2 on the cat and o2 sensors, they can really change the way your engine starts and runs.

Is your air filter clean if it is making noise? Also, vacuume can bugger stuff up. My vac ball was messed up after a rock found it and I had a hard time starting it till it was fixed, not as rough as yours sounds however

Are your engine temps and oil pressure normal?

Chuck

Air filter is not making noise.

remove the cat and start prob broke down that will make it not let the exhaust out kinda like joggin with a potato in you mouth

I am going to get you Muzzy for the English Language.

Engine temp normal, oil pressure is normal most of the time, sometimes slightly higher than normal. Air filter and TB clean, vac ball is fine...its actually way up by my master cylinder. Sounds like I'm going to remove the cat and see what happens. Thanks for all the quick feedback! Probably wont be able to touch it till this weekend but I'll let you all know how it goes.

The Oil Problems is most likely the PCV valve. If it's not connected, there is no provision for blowby to get out of the engine, so it finds a place, the dipstick tube. Next it will push the valve cover or oil pan gasket out. The first problem is the problem your hoping for, the second cause of this is a cracked engine block, usually near the bottom.

Found some time today and I just couldnt wait...I've had this thing parked for a few months now due to a broken wrist so I couldnt work on it.
I just disconnected the Cat and all the problems went away...no rough start...and as for the loss of power...havent tested it on the highway yet but I got it up to 50 on a normal road no sweat...a month ago it could barely go over 30.

And holy ***** is it loud with no cat or muffler! Too bad its illegal and dangerous (fumes venting under the center of cabin...)

Thanks for the help! I was almsot sure it was the fuel pump before consulting hre! Cat cost 1/2 as much and is much easier/quicker to replace.

EDIT: Not sure if the oil spewing problem is fixed but I wasnt as concerned with that...that'll be the next thing I figure out.