Full Size Jeep Network

So my wife has a 98 Grand Cherokee with the inline 6 in it. My problem is that twice while my wife is driving it, it has completely shut off going down the road. It also has an intermittent check engine light for a cylinder 4 misfire. I've replace all the plugs and wires and the cap and button. I'm at a loss as to what else it could be and no one around town has any clue either. Has this happened to anyone else? Does anyone have any better ideas as to what it could be? Any advice would be greatly appreciated. This is our main car and we need it to keep it on the road.

Wild guess, crank position sensor, sometimes a llittle oil leak sends the sensor off, in fact there is a testing procedure for the sensor, it should be between xx and xxx ohms , the engine being at operating temp.
Otherwise check the grounds, as for the misfiring... no ideas, usually it is the specific coil on multicoil engine.

a little search and bammmm

http://www.jeepforum.com/forum/f13/do-y ... or-948246/

or

http://troubleshootmyvehicle.com/jeep/4 ... k-sensor-1

Vacuum leak on #4 runner or the dreaded head crack can cause misfire (check the casting number on the head but it should be at least a year earlier than the cracking ones). Sticky intake valve can cause the misfire as well.

The shutoff can be a few things as mentioned, including a wad of keys on the chain and a worn ignition switch.

She does have a lot of stuff on her key ring. I guess I will replace the switch next. As for the miss fire even when the computer says that is whats happening I can't feel it when driving the Jeep. I also just found out that it's been around five years since she had the coil and plug wires replaced,( we have only been married a year) so that's next one my list of stuff to fix. For now I've put fixing my FSJ to the side so I can keep her Jeep running good so she has a decent car.

My mom's 93 had the suddenly die problem. Based on the research it was narrowed to cps and or coil. Changed cps and coil. Died again after a 3 coils the problem had held off for about 2 years. The last coil was from Chryco. During the research we learned the the wire harness conector to the coil has fitment issues especially with aftermarket coils. Chryco has a repair upgrade kit for the connector but it is impossible to find. There is also an issue with the 98s have bad connectors at the ecu. They will move and cause false codes. Often a bad coil code from what I've been told.

When we changed the last coil also changed the valve cover gasket and cleaned all the oil and grime off. It hasn't been this clean since new.

a bit old, but indeed oil will send bad signals. On the 90 YJ that we had, this is how we fix a bad CPS, change the CPS, but it was so oily, that it makes sense. Bad ground to the ECU is also a known factor.

I have the CPS harness kicking around still. I bought a new sensor from the dealer for $55 and it came with the harness to the CPU cheaper than by itself ($105 alone).

Sorry I never replied guys but it ended up being the CPS. Thanks everyone for all your help.