Diagnostic help with a misfire

Hi

I've searched the forum but can't get any insight with exactly my problem so I thought I'd post and ask for insight. 2006 liberty with 155k miles. oil changed every 3k miles, well maintained. an irregular shudder/misfire has developed between 1k and 2k RPMs. no CEL shows up. did a process of disconnecting the coil packs one by one to try to see if there's one that is misfiring or if we could track down a bad injector. No luck We ran seafoam thru, no change. We installed a new crank positioning switch, no change. Does anyone have any ideas as to what to look at next? I'm confused since it is so random, car starts fine, runs fine, shifts fine, mileage is the same, performace is the same, but it's got this hiccup between 1k and 2k. Any suggestions appreciated! Thanks in advance.

Do you have access to an OBD2 scanner? If it mis-fires you there might be a history for it in the computer.. If it is random and only happens every so often, it may not trip the CEL, but it should store a record of it, along with freeze frame data from the engine.

Hi. I do not have access to an obd2 reader but thats a good idea. I didn't know they stored data. I will check into purchasing one. Thanks for your response. Much appreciated

No Problem.. I picked up an Autel MD802 it is around $100 on Amazon. It has worked very well on Jeep, Ford, Hyundai and Mercedes. How much information is available depends on the vehicle.

Incidentally, I have had issues with intermittent misses on two other vehicles. Both occurred on trips away from home so I didn't have a lot of time to evaluate, but needed to fix then so I didn't get stuck on the side of the road. Both turned out to be ignition issues. I didn't have a code reader so I shotgunned it and replaced all 8 coil packs (Ford Expedition). Problem solved. The other I replaced all the plugs wires.. again got lucky..

Good luck.