Have 96 Xj that's losing and burning oil bad also has a loud knock like piston slap, goes away somewhat when warm. How do i check if its a piston and which cylinder? also want to rule out bad flex plate.

 

Get one of these to pinpoint noises:

 

Here's 2 links on flexplate diagnosis:

https://www.cherokeeforum.com/f51/ho...ocking-125547/

http://www.jeepforum.com/forum/f53/f...-more-2065857/

 

Thanks guys I'm totally going to take inspection plate off again try couple things. I just hope its not engine related if it is, i can fix it, just don't want to tear my motor apart. Besides that tool anyway to single out which cylinder it would be if it was a piston?

 

If our flexplate, and its attach bolts, are good it could very well be a piston slap problem.

If half the piston is missing, up to the oil scaper ring, it would cause oil burning.

If you do have oil consumption problems, pull your spark plugs and see if one or more plugs are oil soaked. It may assit in locating the bad cylinder. See below.

You can isolate which piston it is by removing spark plug wires, one at a time to see which cylinder makes the noise go away, or at least deminish. Do not pull a plug wire while the engine is running (FSM warning). Remove a plug wire at the distributor cap then start the engine, listen for a change in noise. Shut engine down and replace that plug wire and pull another one, repeating the process for all six cylinders.

Some have had luck by unplugging fuel injector connectors to achieve the same results.

#6 cylinder has been the bad guy for many owners so you may want to start there. #1 has been know to have piston pin problems.

If you do think it's a piston slap, you may want to drop the oil pan and inspect the piston skirts. Don't be surprised to see a chunk of piston skirt laying in the oil pan.

 

I did both the spark plug wire removal and injectors. Nothing happens with the wires same noise but when i unplug injector for guess what number 6 lol the noise gets louder.

 

Simple stuff first.

Pull #6 sparkplug and inspect it for fouling (like fuel soaked or oil soaked).

Do the flexplate inspections. Leave no stone unturned.

Not sure what to make of the noise getting louder when #6 injector is unplugged and not with the plug wire pulled, unless there's something wrong with the injector. Try swapping #6 injector with #1 injector and see what happens.

In any case, if #6 is banging away, I think you may end up dropping the oil pan to investigate.