The 4.0l is a very durable and forgiving engine.

Perhaps you are hearing loose timing chain??

or, exhaust manifold???

or, motor mounts??

Those are the only problems I have experienced with that engine in 2 different Jeeps over the past 10 years. One had over 195k miles and my current YJ has 121K miles.

I have never had a problem with injectors. I do run injector cleaner through the engine on a regular basis.

John Stewart
Editor - 4x4Wire.com
Editor - 4x4Voice
Editor - MUIRNet-News
President - BlueRibbon Coalition