Check the casting number of the head

 

ok! what does that have to do with the check engine light coming on though?

 

0331 head usually only found on 00 and 01 had casting defects allowing for cracking and compression failure, high oil and coolant consumption and lead to CEL

 

Could be a bad sensor. My TPS just went bad the other day. Let us know what the error code is.

 

Update (2/10/25) -
Good news! nothing super major is wrong with the XJ! The issue reads as a 301 error code on the autozone computers. Looked up common causes of the 301 code, came up with a bunch of different results.The most common of these being a need for new spark plugs. so i grabbed some new spark plugs, engine oil, oil filter and changed all that out. cost me a total of $66. turned her back on drove her around for about an hour nearly 25 miles, computers had adequate time to reset after disconnecting the battery and no more check engine light! wish me luck hopefully everything continues to go well and run smoothly.

 

That being said, i would love to know if a bad TPS sensor also causes the 301 error code/piston misfire?

 

A TPS failure wouldn't throw a PO301 code, A bad sensor wouldn't cause a misfire. Glad you figured everything out!

 

While I firmly believe that a misfire code is a symptom of a deeper problem I had a P0304 once.
Figured easiest thing first so I replaced the plug.
Sure enough.

 

that's interesting. what does the P304 code mean? And how come you believe a misfire is product of a deeper problem?

 

Misfire on cylinder 4.
Read a fair amount about guys having misfire codes on the forums and new plugs, wires, coil, etc don't seem to solve the problem sometimes.
They are basically shooting the parts cannon at the problem.
I keep plugs in "stock" so figured it was worth a shot.
But if that did not solve the problem would have tried to figure out what is going on before anything else.

 

Update (2/11/25) -
Been driving the XJ as I typically do. No more profound issues, no overheating or check engine light yet. crossing my fingers that it stays that way! will be changing the coolant soon.

 

ah ok!

 

Update (2/12/25) -
Considering getting a new aftermarket electric fan for the XJ, may even go off on a side quest to absolutely obliterate the potential of overheating in my Jeep! However i will need to work that side quest into the process of welding on some mid frame stiffeners, and getting the whole Jeep undercoated, which i will be starting very very soon!

Question: does driving slower make the engine work harder, and in turn cause more frequent overheating?

 

You mean like rock crawling speeds or driving in the city?
What product are you planning to use for undercoating?

 

primarily driving in the city. a lot of stopping and going at the turn of lights.
and i was considering fluid film but because i also plan on welding on some mid unibody frame stiffeners i think ill just go with something more permanent like rhino liner or raptor liner. Do you have any suggestions or gripes about either of those, i am open to suggestions!