2002 Mercury Mountaineer 4.6 V8 runs rough when hot No codes present I have changed all 8 plugs 1 coil air and fuel filters to no avail Has anyone seen this problem before?

A rough-running engine when hot, especially without any diagnostic trouble codes, can be indicative of several issues. Potential causes include a failing fuel pump, clogged fuel injectors, or an issue with the ignition system that may not have been addressed by changing the plugs and one coil. Additionally, consider checking the coolant temperature sensor, as it can affect fuel mixture when the engine heats up. If these components are all functioning properly, a compression test may help identify internal engine problems.