I have a 98 wrangler sport with a 4.0L The problem is when you start up the jeep after about 30 to 60 seconds it starts to idle pretty rough and if you start to drive immediately after about a half mile it will start to buck wildly and has no power when you step on the gas. It is a five speed and when it is bucking and loosing power if you push in the clutch you can rev the engine. I have replaced the cap rotor wires and plugs also have two new o2 sensors to go in. I have read a few things about this engine needing the distributor to be indexed and the crank sensor going bad. If anyone has any information that could help me that would be great. really frustrated with this one thanks

I had the same problem with my 88 Cherokee. It was my CPS (Crank Position Sensor) plug. I unplugged it and plugged it back in, about 3 times or so. I guess dirt and junk can get in there and cause a bad connection. Try that. OH, the CPS is on the driverside of the engine at the back, on the upper part of the bellhousing. Does your check engine light come on? If so, check the codes, it can tell you whats wrong. Let us know what you find out.
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OH, also check the TPS (throttle position sensor) on the throttle body. Check the factory service manual for the proper way to test it. You'll need a voltmeter to check it.