97 4.0 dies for no reason

[mud slinger]

Over my head and need the experts again. My 97 tj 4.0 is acting up and cant figure out. Its actually a 93 block with all the 97 parts to make work in 97. The distributer and coil are still from 93. Mostly it runs great. Recently it has been acting like it has a carbrater and the choke sticks. It will be idleing fine then it will start missing sometimes it will run like crap for a minute or two then rev up a little and run fine. No matter what i do with thrittle it acts same. if like when im on a trail hill and it starts it will pull itself but misses like crazy. Stop shut off for a minute then will start up and run like nothing happened. I put new tps in no change put new fuel pump in about 4 months ago. checked dist cap and no visible cracks or anything. I dont know how to check things like the pic up in the dist or coil. seems to do it mostly in a low rpm or idle. Spring is here finally and im afraid to take in woods or to work for that matter. any advice please thanks

[Bill Cooke]

A miss like that usually means something in the timing is off. That could be many things with a computer controlled engine. It could be a loose crank position sensor, cam sensor or something like that. I would have said TPS or fuel pump myself but since you tried those look at something electrical on the engine. It could be a shorted wire too. Pay close attention to things like weather and time of day too. If it does it when it's cold out or only when it's warm that can tell you things. Rain and a miss almost always means a leaky distributor cap or a bad plug/coil wire.

You should also be able to get codes on that Jeep. That can help track down problems but it might not. Intermittent things like this can be hard to diagnose, as you know. Just check everything with a wire hooked to it. Temp sensors and all. Something is not sending the right signal to the computer and it's tripping it up. Pull every connector apart and check it for corrosion or anything like that.

Hope this helps. Post more if you want more help figuring this out.

Bill Cooke