Not satisfied with the answers I'm getting on Jeepforum. Check the pics in the thread. The plastic piece is just one piece, I just tried to get pics from different angles. It's about 2" x 1" square, but it likely broke off something larger.

Jeep Wrangler 4.0l inline six.

Thread here:

http://www.jeepforum.com/forum/f12/help-me-identify-what-i-found-my-oil-pan-pics-1359139/

any ideas?

It seems weird that there would be something plastic in the engine that could get into the oil pan. Was there anything in the oil filter?

People on forums for other kinds of cars are guessing timing chain guide too but would that have a set screw in it?

Ball plunger. Used to produce a detent action on a sliding part. Refined versions hold sockets on ratchet wrenches.

If you still have the last oil filter, you might autopsy it for more bits of junk.

Do you have a pic to confirm how the screw fits agains the plastic bit?

Could have been worse

Click thru on item 40 - could that have been the part?

That's the only thing I can fathom it being also. The piece I have clearly has some grooves in it that aren't in the pictured one, but that could be simply the OEM vs. aftermarket thing.

I also can't see in the pictures where the ball plunger screws in, and there's a place on mine for it. You can kinda see it in the lower right picture. A hole on the upper right edge where the ball plunger screws in diagonally. I'll get a picture of the plunger partially screwed in when I get back to the village. (I'm in the city for shopping now).

those ball things are also used to hold the thumbwheel in on adjustable wrenches.

It's also possible that someone that worked on the car broke a tool and the pieces ended up in the oil pan.

We shot a transmission with a good sized round while it was running, and had it continue running for 30mins afterwards. It didn't have as much debris as that timing chain when we pulled it apart.

Thanks guys. I ordered a new timing chain and guide since it's about time to swap it out anyway. We'll see what it looks like.

One thing that cushions the blow a bit is that I'll likely pay about $50 in labor to get it swapped. There are some benefits to living in the majority world .

While you’re in there you might consider putting in a hotter cam if you’d like a bit more performance. Make sure to get new lifters too.