My guess would be components in the rear brake assembly. My 2003 Liberty kind of makes a creaking sound back there. Depending on the type of sound it might also be something with the exhaust system, which I believe runs down the passenger side.
I would suspect the spark plug wires are installed incorrectly on the passenger side.
Unburned fuel in the exhaust system causes the backfire from the exhaust pipe.
I think you are hearing pressure pops. Not a backfire.
a backfire is caused by incorrect timing or not enough back pressure in the exhaust pipe
It's lean.
It's lean.
Backfire is normally caused by engine out of time, or spark plug wires installed incorrectly.
bad gas
Out of time.
Too much PSI.
Your car is running too rich.
As with any engine, timing, and also carb problems.