1994 Mercury Sable Q&A
1994 Mercury Sable Question: rough running engine missing
The most likely cause of this for your vehicle is ignition wires. As they get old and weathered the spark starts to leak to ground instead of go to the spark plug as it should, this causes the intermittent jerk surge or rough running. Spark plugs and wires were to be replaced every 60,000 miles on this vehicle so if you have not changed them within these ranges, you should consider changing both items. If you do change the plug and wires, you should inspect the condition of the distributor cap and rotor and replace as necessary. Those are the things I would check or replace first.Good luck. - irvtech
Engine sometimes is ruff at idle. Missed and hesitate when driving up a hill. Ample supply of gas in tank. MPG has dropped from 19 to 16.