• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Disabling individual cylinders on a 2001?

anthrax323

NAXJA Forum User
Location
San Antonio, TX
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?
 
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.


Sent from my iPhone using Tapatalk
 
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.


Sent from my iPhone using Tapatalk


Instead of pumping unburnt fuel into the exhaust, you'll be pumping fresh air, so may see different associated lean/rich codes get set.
 
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.
 
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.
 
Yeah... I was just beating around the bush.

Dropped the oil pan...

skirt.jpg


Hello there, piston skirt. A little pissed off now. Looks like I'm building a stroker.
 
Glad you found it. One of my fears as well.

Once repaired, that stroker should be lots of fun.
 
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


Sent from my iPhone using Tapatalk
 
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!
 
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.


Sent from my iPhone using Tapatalk
 
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.
 
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
 
Back
Top