Pulling the spark plug wires off of the spark plug is really not difficult and doesn't require tools. The point of doing it is to run the engine with one cylinder loafing (not firing) to see if the noise goes away when one particular cylinder is affected. That can help you isolate a noise to a particular cylinder. If the noise does not change after trying it on all 6 cylinders then you would have to look at other systems to see if you can identify what's causing the noise. It may be better to pull the plug wire off when the engine is not running so that you do not risk a shock or get yourself tangled up in the moving components.

 

I would rather pull a plug wire (non-running engine) than mess around with those fragile plastic clips on the injectors.

 

Looks like the wrong part to me. The picture here is of the correct AZ part for 4.0L with gauge (from AZ's website).... part #PS358

 

No metal found in the pan? If you find that the noise gets louder, I'd pull the pan again and look for yourself. Immediately. Sounds like a rebuild is in you're future one way or another. So it really becomes about damage control at this point. I could very well be wrong, but I'm leaning towards engine damage. Keep us updated!

 

Having gone through all the posts, and listened to the videos, I really think it's just piston slap. The frequency is too rapid for valve clatter or a stuck lifter, which would only click half that fast. There's a noticeable difference between the sound of the piston slap and loose flexplate or flywheel bolts. That noise is much shallower, and the piston slap noise is deeper in the engine mass. Also, the former will not quiet down as much after warm-up, whereas the piston slap will. Piston slap is not at all uncommon on the 4.0L, especially those beyond 100K. Also nothing to be concerned about, since it'll likely go for another 200K+, as long as you continue to care for it otherwise with decent maintenance. My '90 has 260K on it, has had the piston slap for 10 years or so, and I can only hear it in the winter when the truck hasn't been driven for a couple days. I just drive it easy until it warms up a bit. It quiets down after 3-4 minutes. I use either 10W30 or 0W30 full synth, and have since it was new. I change it just once a year, usually around 8000-10000 miles.

 

Thank you for taking the time and your informed opinion.

 

Update - I have not had the time to mess with the flex plate bolts but I did change the oil.

So right now here is what it sounds like with the only change being putting in Brad Penn 009-7126-12PK 0W-30 Partial Synthetic Racing Oil.

The noise is gone at startup, if I let it sit and idle the noise pops up around 1:15 (all on the video) but is not nearly as loud or noticeable as it was previously. Could the oil have any affect on this or is it coincidence? Note that phone is under the Jeep for this video, noise is no longer evident at all unless you are under there listening.

 

Sounds like a rod knock but certainly not loud enough to worry about. That been said, I wouldn't put anything less than 5W-30 in there. If you're adamant about using synthetic, use 5W-40 but if it were me I'd go with regular 10W-30 and a good quality filter.

 

I'm betting that the noise is coming from the valve train.
Most likely caused by the hydraulic valve lifters.
It sounds like your engine has a little "play" (lash) between the lifters and valves until the oil pressure builds and stabilizes inside the lifters.

That sound is the valves tapping.

You say you got a new cam and lifters?
What brand and part numbers?
Did the mechanic also replace the push rods?

 

Here is what I have for service history from PO, I find nothing about push rods -

8/17/13 @ 160,133 miles
Note says "Check engine knocking when first started".
They replaced head gasket, head bolts, valve cover gaskets, camshaft, lifters, thermostat, timing chains, gears, timing gasket.
Part numbers are:
Camshaft MC1377
Lifters JB-2011
Timing Set 3-385SB
Intake Manifold 123
Cost: $1,653.70

1/25/14 @ 161,928 miles
Note says "Check for headgasket leak - customer has been adding antifreeze thinks it is mixing with oil - headgasket replaced here last year".
Here they replaced the head, says they found crack between #3 and #4 cylinder, so apparently they thought it was just a gasket but turned out to be the head or the head cracked in the previous 5 months.
Part numbers are:
Cylinder Head 2A34
Head Bolt Set ES71102
Cost: $962.92

No idea how long it ran with the cracked head, doesnt say that PO complained of coolant loss @ 160,133 miles but did @ 161,928.

 

A few observations:

1. I would bet the infamous 0331 head was cracked already the first time the shop worked on it. Then it came back around and bit them in the *** just a short time after putting it back together. These heads do that with alarming regularity.

2. Your should never put any kind of racing oil in a street engine. It is not better for it. It can and will screw up a street engine pretty quickly. I also personally would not be experimenting with viscosity at this point. A poster named "salad" should be along here shortly to explain this. He is the oil guru around here.

3. Like a poster said just a couple of entries up, and as I said early on, it just sounds like a thrashy valvetrain. Did you do the tests I suggested earlier?

 

Haven't had time to do anything but oil change. I have read lots of good on Penn oil in Jeep 4.0 due to high levels of ZDDP plus has detergents, only thing I have seen is it could damage cat converter but read nothing but good about it in engine and it seems to have helped.

If you read the reviews on amazon a guy specifically mentions it made piston slap in his corvette go away.

 

Did u ever remove the valve cover to inspect for obvious oiling issues? Only takes an hour or less. Push rods can be removed/inspected/cleaned, the rocker arms can inspected and the rocker bridges can be re-torqued to proper spec when the valve cover is off. Post pics of the valve train with the valve cover off.

 

Five pages, 73 posts, and all that has been done is an oil change.

 

I am a lot more educated and can better understand when mechanic checks it out. Believe me if I was capable of doing more I would, very hard when I am driving everyday and something that may be simple for you could take me days.