Ok, so I bought my wife a 98 xj last week test drove it seemed great but every so often while driving through town it chokes and the only way to get it going again is to put it to the wood for a few seconds..I also noticed this thing gets severely hot within minutes of driving.. the gauge stays right on 210 where it should but motor and hood are very hot and you can just see the heat rolling off the cat... Could the cat be plugged causing all the heat and choking? New plugs and wires have been installed guy i got it from said it sat for a while so I put some sea foam in yet but still no luck... Bare with me all I've ever owned in life were diesels so this is new to me... Thanks!!

 

that's absolutely a tell tale of a clogged cat...

shoot it with an IR temperature gun... they're cheap and hella useful. aim right before the cat (like, and inch) and then right after the cat. the temperature shouldn't vary by more than 25* or so... if it's hotter prior, you've got a breathing issue... THIS is the easiest cat test known to the western world... the japs cram tiny engineers in there, and if they don't come out it's clogged.

now... why is it clogged? they are designed to get hot... they draft exhaust and actually speed up the conveyer of pulses through them- an area of low pressure that begs to be filled (like my ex girlfriend)- it almost makes up for the obstruction it creates by getting hot as it does- almost...

the catalyst supposedly (according to dudes who wear white coats and carry clip boards) scrubs the nitrox, capturing it and burning it... I don't know about that.. but what I do know? zinc clogs them with a quickness... zinc (ZDDP is the Z in that compound) is a common additive in oil... oil gets into the combustion process most commonly by having bad valve seals...

in short (already blew that, no?) if your kitty is clogged, it is a symptom of the problem, not the problem itself... it has to be replaced if the temp test fails, and then you need to see what caused it... oil, most likely... could be coolant, too- but coolant will DESTROY an o2 sensor with upmost quickness, so a coolant leak into the exhaust is usually manifest by CEL's pointing to o2's....

 

Put it this way,i can spit on my tail pipe and it sizzles

 

bravo this was very entertaining, thank you. I would like to add that if you have excess fuel (unburnt) leaking and making it into the exhaust stream it will superheat your cat and cause it to fail. A leaking injector could wash the cylinder walls out making it passed the rings and diluting the oil causing oil blow-by thus making it's way into the combustion chamber and into the exhaust. Gasoline-diluted oil will wipe out your lower end too. Pretty vicious cycle.

This should sound a little familiar to the OP if you're a diesel guy. Excessive fueling causes what? HIGH EGTS! Very good class. Essentially, raw fuel isn't good for gas engines either.

YOUR TAILPIPE?! It shouldn't be anywhere near that hot.

 

Put it this way,i can spit on my tail pipe and it sizzles

 

Don't worry about the hood, they're all like that.

Any codes?


chokes and the only way to get it going again is to put it to the wood for a few seconds.
What's the fuel pressure in psi?

New plugs and wires have been installed
Cheapy parts could have a dead cylinder plus confirm the firing order

 

Got a number Drew?

 

just don't get attached.... treat that one more like fuel, or tires at the most- in contrast to wheels and engines... she's gonna get filled whether you're present or not... other than that, it sho nuff were fun....