rough idle

I have a 01 Explorer Sport(4.0L SOHC)with 93,500 miles on it and it idles rough. I have changed out the fuel filter,air filter, plug wires, spark plugs, ignition coil(resistance on the secondary coil was out of limits) egr valve, dpfe valve, egr solenoid, fuel injector cleaner every 1500 to 3000 miles, new muffler, cleaned out the idle control valve(also checked the resistance on the solenoid and it was fine). i even hooked a vacuum gage to it and it is reading 18 inches in Hg. Has anybody had a similar problem? any help would be great.

get the charging system fixed then see what the idle does.

well ichanged out the tps sensor. the rpm has gone up and and the rough idle has gone away to some degree. still idles a little rough, but iam thinking it could be bad motor mounts, i will check them this week.

oh charging system was fine