Cant figure out what is going on. I have a 99 cherokee that has the 4.0. It is popping through the intake, when it and if it starts it wont accelerate and runs really rough and also smells like it is running rich. I have replaced crank sensor. Idle air control. Throttle posting sensor and it made it run worse. Feels like it has no power either and info would be great.

 

Any check engine light? If you have one on or even have seen one, you must retrieve codes for clues and guidance as to how to proceed.

If there are no codes, job #1 is to test fuel pressure. Must be done with a gauge, which can be rented inexpensively from many parts stores, call around. Easy to perform this test. The fuel pressure spec. for the 99 is 49 psi, plus or minus 5 psi.

There certainly are a number of other possibilities, but don't throw any more parts at this. Adopt a "testing based strategy" to determine root cause and fuel pressure is tops on your list.

Good luck and keep us updated!