So my 4.0 has a slight knock started about a week after I got it put a bout 1200 miles on it was told it was piston slap. So I've changed the oil with a standard pure one filter should I use a mopar maybe. I've did the pulling the plug test no change but about 15 min ago I pulled the injector plugs and the back 2 when I pulled them the knock got somewhat louder what is it???

 

Connecting rod bearings, broken and/or cracked flex plate? Piston slap in usually loudest in cold weather & goes away entirely when the engine is warmed up & in warm weather.

 

If its rod bearings can u just pull the pan and change them on a 4.0

 

If the rod bearing are kaput, all the bearings are.

 

It use to quiet down once warmed up but now it dosent and I checked the flexplate and didn't seem to have any cracks around the bolts but I did not try to tighten them.