OK my 98 XJ 4.0 stutters and runs rough. I give it gas and it stutters and sounds like a motorcycle. But the weird thing is after driving it for about 30 seconds it clears up and idles fine. It smells like fuel when it stutters too. Last tune up under 10k miles

 

Is this when the motor is hott? Or all the time?

 

OK, I actually found it. (in a 99 FSM) If the fuel pressure drops from 49 to less than 30 in five minutes, injector/s might be leaking. That might do that, something to check. May well be free to borrow a gauge at the auto parts store. (I buy at Napa, but borrow at Autozone).

 

I think that would be as good a place as any to start quick and easy, with an easy fix also if its an injector leak.

 

The fuel leakdown test will tell you if your pressure is dropping or not, with the criteria as stated above by DFlinstone.
In case it does drop below that, you need to test further to differentiate between the injectors being the cause or the drainback valve(s) being faulty. That procedure is outlined in the FSM as well.

 

Well my jeep stumbles until it warms up. I'll start it up and it sounds like a motorcycle popping when you give it gas. I'll drive it down the road and after about 30 seconds it clears up and runs fine. smells like gas when it stumbles. Also if I cut it off and cut it back on it won't start up. It'll get up to 200 rpm and just die. But if I try and start it again it runs and still stumbles. I've replaced the IAC, TPS, cleaned the injectors, done a complete tuneup.

 

Did you do the fuel pressure leak down test? With what results?