Good morning all. I'm at my wits end and need your guidance. I have a 1998 Nissan Pathfinder LE 4x4 AT and am having noticeable misfiring between 0 - 3000 RPMs along with little power; but exactly at 3000 RPMs, the engine comes to life and has alot of power and no misfires. I was having this back in January and then while on a trip, my radiator plastic top split right open. I had it towed to the closest Nissan dealership to have it repaired. After putting in a new radiator, changing out the engine from a 140K to an 80K due to a blown head gasket and possible cylinder damage, and new plugs/wires/distributor w/ cap&rotor, I still am getting the random misfire. I do not have any vacuum leaks, the fuel pressure is good, and I am not getting any other error codes. The dealership had it for three months and could not figure it out.

I am thinking about changing out the ECM under the dash, or maybe having the exhaust looked at... Am I on the right track?

Charles