Im looking at this xj on craigslist, and the guy is asking $800 obo. The jeep was recently painted, and has new michelins on it. It is a manual, which is also a big plus. The jeep runs, but the owner says that it has a knock in the engine. I am really just wondering what questions i need to ask him to help diagnose the issue, to see if its worth buying or not. It has a manual 5 speed, 4.0L I6

Tranny and engine have over 200k miles on them, and he said its a loud knock in the engine. He says it has never overheated, "oil pressure is good off of idle, 35-40 psi at idle" and that teh noise is more when the engine is warmed.

from those details, can you tell anything? if not, what other information should i ask him for. Thanks for the help guys

 

There is a Knock Sensor that could be unplugged or out. It is at the bottom driver side of the engine. Well above the oil pan portion.

Other than that I would stay away from it. Or offer him 3-400 bucks and drop a new engine in it.

 

Look at the this link and scroll down 3/4 of the way and you will see some knock sensor info.

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

 

Is there a way that I can see if the knock is the bad sensor instead of say a broken piston? And what's it cost to replace something like that

 

THe knock sensor or a broken piston.

Knock sensor I dunno a couple bucks at vatozone.

Piston... Just get an new refurbished engine at 1500. cost ya more in labor to fix that i bet and you still have the problem of it being a old engine.

 

The knock sensor is only there to retard the ignition timing should pinging occur.
That ain't the issue here.
Plan for the worst and hope for the best. Used motor? Offer him $200 and see what happens.

 

What type of tires?
A set of (4) Michelin LTX A/T 2 P235/75R15
OTD ~ $650 from Discount tire. + Just plan on a new motor.

 

Good point. You're more generous than I when negotiating. LOL.