You can't repair them...only replace them. Any auto parts store can get them and they're not too expensive.
Usually if it is trans-mounted the one closest to the passenger side If it is conventional the one closest to the front of vehicle
A four cylinder engine can be built to be EXTREMELY powerful, either my machining of the physical metal (head and block) to allow for more cylinder displacment and volumetric efficiency, or by use of...
First one opposite the transmission end.
it could be as minor as a tune up (spark plugs and wires)(or bad distributor coil pack). or possibly a faulty fuel injector.
NOT IT,S A DUKE CAST IRON