Nissan Repair: Intermittent engine problems, nissan 240 sx, 1995 nissan 240 sx

Question
I have a 1995 Nissan 240 SX with 130K. The car runs like a dream, but at times, especially on the highway over 65 MPH, the car will start bucking for a few seconds to a minute. (Sometimes violently) It is almost as if the gas cuts off and/or is intermittently spurting. If I keep the gas constant, it is much slower to stop the bucking than if I take my foot of the gas completely for a few seconds, then slowly apply pressure to the pedal. After a while, it runs like a dream again for miles. I've changed spark plugs twice and used premium Amoco gas only for the last 10 fill-ups, but evidently it is not a gas quality or spark plug problem.  Thank you very much, Dave  

Answer
Fave,

If the car has a distributor it probably has oil on the optical pickup.  This is what signals the computer to fire the plugs.  It is under the cover that is below the rotor.  If there is oil inside you found your problem.  After many years the internal oil seal fails and the pickup gets screwed up with oil blocking the optics.