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Whats this sound?

Spruce

NAXJA Forum User
2000
4.0
automatic
170k

I have been chasing a cylinder 6 misfire for a few weeks, and I finally had time to swap the coil, plug, injector, and clean all the engine grounds this weekend. Prior to me messing with it the clicking/tapping sound didn't exist. I've heard lifter chatter, and I think this is too loud to be that...please help me identify the sound.

*note - The engine was on for 5-7 minutes while I tried to figure out where it was coming from and shoot this video. I'm hoping that's not enough time to actually ruin anything in the engine if somehow I've managed to muck things up.

https://youtu.be/xlXOCv6W5NY
 
Are you still getting cyl 6 misfire CELs after changing all those parts?

Maybe an exhaust leak?

Might want to double check the coil pack installation.
Not all that hard for one of the coil pack's boot to totally miss the spark plug causing a misfire.
That coil pack idea was one of the worst things ever done to a 4.0.
 
Did you replace all the plugs, injectors, coils?

What brands and part numbers? Are they the absolute correct ones. If the plug isn't there's correct one, a real possibility exist that it's hitting the tip of the cylinder.

If the noise wasn't there before you replaced said parts, it is very likely it's something you did.
 
Not all that hard for one of the coil pack's boot to totally miss the spark plug causing a misfire.

That coil pack idea was one of the worst things ever done to a 4.0.

Never had any issue with that in 20yrs!

Interesting coming from you, "engineers don't make mistakes, they only make revisions". Woo-woo!

The idea was good from a PCM standpoint, they just didn't think it thru until the JK. https://naxja.org/forum/showthread.php?t=1156312
 
Did you replace all the plugs, injectors, coils?

What brands and part numbers? Are they the absolute correct ones. If the plug isn't there's correct one, a real possibility exist that it's hitting the tip of the cylinder.

If the noise wasn't there before you replaced said parts, it is very likely it's something you did.


I Replaced all of the plugs with NGK's recently, but re-replaced cyl 6 with a champion because I thought it may have been a bad plug (PN -RC12ECC Champion Plug). The injector is a factory oem from a 99 XJ.
 
Are you still getting cyl 6 misfire CELs after changing all those parts?

Maybe an exhaust leak?

Might want to double check the coil pack installation.
Not all that hard for one of the coil pack's boot to totally miss the spark plug causing a misfire.
That coil pack idea was one of the worst things ever done to a 4.0.

The misfire code didn't pop up in the very few minutes that I was running the engine, but even before I could pull the battery negative and drive 50 or 60 miles before the code came back. I just went out and checked that the pack was seated correctly, and it is.
 
What CEL Trouble Codes are occurring or were downloaded ?




I just went out and checked that the pack was seated correctly, and it is.

One might suspect that the coil rail or the wire harness/wire plug has developed a fault. They can be tested.


Might want to double check the coil pack installation.
Not all that hard for one of the coil pack's boot to totally miss the spark plug causing a misfire.

Happened to me once.
 
Last edited:
Might want to get a cheap automotive stethoscope from HF or use a screw driver to pinpoint exactly where the noise is coming from.
It does seem from the video the noise gets louder towards cyl. 6.

If you localize the noise around cyl. 6 its something you did, a coincidence waiting to happen or the misfire was caused by a weakened broken valve spring, rocker arm, etc. that finally let loose.
As a last resort i'd pull the valve cover and have a look.

Does the noise change with rpm?
Does the noise get quiet when the engine warms up?
 
I would remove the valve cover and check all the rocker arms and push rods , If they all look good I would run the engine with the valve cover off , it will make a mess but you can see if all the rocker arms are moving the same . If all is good them maybe you have a broken piston skirt .
 
What CEL Trouble Codes are occurring or were downloaded ?






One might suspect that the coil rail or the wire harness/wire plug has developed a fault. They can be tested.




Happened to me once.

Thanks for the help guys. The only code that was thrown was a p306. I'll have to wait until the weekend to pull the valve cover as it's dark when I get home from work, but that seems to be my next move
 
So i dodged snowflakes long enough to pull the coil and plug again, and found that the new plug had been scorched pretty good. I swapped it for a spare NGK that I had and it seems to have quelled the ticking I had. Now it's just got the normal lifter chatter. I think it's unlikely that I had the old plug installed incorrectly...I torqued to 27lbs, and it was gapped correctly. I'm hoping the misfire is fixed, but even if it's not maybe I figured this one out.

Pic of plug with 0 miles and 10 minutes at idle on it

m8ZAEShh.jpg
 
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