Nissan Repair: 1993 Nissan Quest engine misfires, quest engine, nissan quest

Question
I own a 1993 Nissan Quest and the engine is running rough.The RPM is 850 rpm idling or 4000 maximum rpm if I use the gas pedal, no matters how hard or easy I press.The engine is running at a variable rpm from what I hear, but the gauge is showing constant rpm of 4000 or 850 when the gas pedal is not pressed.

Answer
Aristotel,

First, the basics like change the spark plugs, wires, cap and rotor.  But, from my experience it will be the distributor itself since the age of the vehicle.  The distributor has an optical pickup and receiver under the cover that is under the rotor post.  This gets contaminated with oil as the seal allows oil to wick up the shaft.  A rebuilt distributor corrects the problem.