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1999 ford contour runs fine until driving nonstop for more than 2 hours

Almost everytime I drive the car for more than 2 consecutive it acts as if it drops a cylinder…running rough … the next day it will run fine until 2 hours go by…and so on I have changed plugs wires and coil pack … any thoughts are helpful 4 cylinder automatic

My first thought is a possible intake manifold air leak or perhaps a faulty O2 sensor. Maybe a MAF sensor possibly or bad engine electrical grounding. See if anything shows up using a vaccuum gauge.

Fuel filter? weak fuel pump? Does the CEL ever come on?