1994 Ford Explorer car idle go's up and down on it's own

You may have a vacuum leak, get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs! Check also fo unmetered air from the air intake plenum betwwen the air filter box, all the way up to the throttle.