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anthrax323
November 30th, 2017, 09:25
Hey guys,

Does the PCM on the 2001 XJ support any OBD2 mode 8 functions? I'm trying to pin down which cylinder is noisy (it's a bad rod bearing, wrist pin, or broken skirt... not sure which yet) and can't just pull a single plug wire since it has the coil rail.

Would disconnecting the injector accomplish the same task, more or less?

blakews2217
November 30th, 2017, 15:29
Hey guys,

Does the PCM on the 2001 XJ support any OBD2 mode 8 functions? I'm trying to pin down which cylinder is noisy (it's a bad rod bearing, wrist pin, or broken skirt... not sure which yet) and can't just pull a single plug wire since it has the coil rail.

Would disconnecting the injector accomplish the same task, more or less?



It would. Your taking one of the things away that it needs. ( fuel, spark and air. Your taking fuel). But it will throw a code for open injector circuit.


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lawsoncl
November 30th, 2017, 21:16
It would. Your taking one of the things away that it needs. ( fuel, spark and air. Your taking fuel). But it will throw a code for open injector circuit.


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Instead of pumping unburnt fuel into the exhaust, you'll be pumping fresh air, so may see different associated lean/rich codes get set.

Saudade
December 2nd, 2017, 09:43
Yes it will.

Or you can use a long blade screwdriver. Press the tip against the engine and your ear to the handle. This will magnify the noise. Move the screwdriver around until the noise is the loudest.

You will also hear all sorts of other noise so don't be too alarmed.

Greenz
December 3rd, 2017, 09:29
Hey guys,

Does the PCM on the 2001 XJ support any OBD2 mode 8 functions? I'm trying to pin down which cylinder is noisy (it's a bad rod bearing, wrist pin, or broken skirt... not sure which yet) and can't just pull a single plug wire since it has the coil rail.

Would disconnecting the injector accomplish the same task, more or less?

Why not just drop the oil pan and look? Knowing the offending cylinder number doesn't fix the noise until the engine is opened anyways.

I'm asking out of curiosity for my lack of wisdom on this one.

anthrax323
December 3rd, 2017, 12:44
Yeah... I was just beating around the bush.

Dropped the oil pan...

http://flargen.com/images/jeep/skirt.jpg

Hello there, piston skirt. A little pissed off now. Looks like I'm building a stroker.

Greenz
December 3rd, 2017, 17:55
Glad you found it. One of my fears as well.

Once repaired, that stroker should be lots of fun.

anthrax323
December 3rd, 2017, 18:10
It's an unmistakable sound. A lot like rod bearing noise, but way louder and more clacky.

blakews2217
December 4th, 2017, 10:00
It's an unmistakable sound. A lot like rod bearing noise, but way louder and more clacky.



I can tell you what it sounds like when a 0331 head really does damage. I bought a 2000 xj with really bad rod knock. Pulled it and opened it and found a missing piston in a million pices in the pan and the rod just hammering away in the cylinder. My best guess is this

Ran hot, cracked the head

The crack opened far enough to allow water in from the coolant passage during the downstroke of the piston and filled the cylinder with coolant.

Piston starts to move up but water can’t go back fast enough through the crack. Piston hits it max pressure it can withstand and breaks around the rod and falls.

Piston pices and lots of water hit the hot oil pan

Gets sold for 800 bucks to me


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Greenz
December 4th, 2017, 10:39
My sons Prism just broke a piston rod and then pushed it through the bottom of the oil pan puking oil and metal bits. That was cyl #4, Cyl #1 was full of oil fouling the plug. The darned car still runs on two cylinders but makes a whale of a noise. We laughed so hard over that poor little car trying to live. LOL!

blakews2217
December 4th, 2017, 13:07
My buddy bought a 94 v6 dakota to learn stick in. We were going to his moms ( we’re 18/19 years old) and right as I turned the corner it threw a rod through the pan. We drove it back across town to my house and proceeded to try to kill it. It ran for a few more days till it ate a big handful of floor dry. Fun times.


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BCKNBLK
December 5th, 2017, 21:30
Hey Anthrax, just went through your situation myself, mine was the number 6 piston skirt. Rebuilt the entire engine (but not stroked) and went with a hotter cam. All quality parts this time, not like the original junk. It should outlast the vehicle now, runs really great. If you need any advice, help, hints, pointers, etc, let me know while this is all still fresh in my grey matter.

anthrax323
December 6th, 2017, 16:25
Hey Anthrax, just went through your situation myself, mine was the number 6 piston skirt. Rebuilt the entire engine (but not stroked) and went with a hotter cam. All quality parts this time, not like the original junk. It should outlast the vehicle now, runs really great. If you need any advice, help, hints, pointers, etc, let me know while this is all still fresh in my grey matter.
Thanks man, much appreciated! I'm tearing it down now and getting ready to figure out my plan of attack. I'm documenting it here since I'm already running into some weirdness:

http://naxja.org/forum/showthread.php?t=1145305