Hey from Canada Scotty!
I recently purchased a 1997 Jeep Cherokee Sport with the 4.0 engine and auto trans. The Jeep has 208,000 km (129,000 mi) I am second owner and know the original owner well. It’s in mint condition and babied on road it’s whole life. My question is: There seems to be a slight miss at idle but has clean acceleration and no miss at driving speed in the city or highway, basically it otherwise runs perfect. I borrowed a scan tool and there’s no codes and no misfires show up in the count at idle yet you can hear it missing randomly. I installed cap, rotor, wires and plugs with no change....Any ideas? Thanks for your time sir!
Brad
New parts can't be assumed to be good, especially with things like distributor caps, rotors, and wires that have not been seen on most new vehicles for 20+ years and are now low-production items. Maybe pull the plugs after idling for a while (letting engine cool of course) and see if one is loading up with carbon. You might try a spark plug test light to see if they're all firing OK. Also look at spark plug wires in the dark while engine is idling to see if they're leaking spark to ground or other wires.
https://www.youtube.com/watch?v=UymD_i_9Q9Y
