It has been acting weird for weeks, the 2nd cylinder from the left misfiring when we stopped to sit at a light, then fixing itself to running on all 4 when we started driving. Now, its only running on 3 no matter what we do. Does this sound more like the spark plug, or the spark plug wire that runs to the plug?
My car has 233000 miles.
My car has a manual transmission.
Any time you have a misfiring cylinder the easiest thing to do is to replace the spark plugs and check the plug wires to see if valve cover leaks oil onto plug wires in spark plug holes. If it does then replace valve cover gasket, plugs and plug wires to fix the misfire.