Misfire at idle runs rough on 1994 Mazda B4000

94 mazda b-4000 misfires at idle have changed egr - o2 sensor - plugs wires coil pack all have given more power yet still misfires. it appears to run more rough at times

Some times at highway speeds the speedomator will jump about 5 mile per hour.

Asked by for the 1994 Mazda B4000
Check for any vacuum leaks. These can cause misfires at idle that will smooth out when you are on the road. When I say vacuum leaks, I also include a leaking intake manifold. And, if you ever get a check engine/service engine soon light on, be SURE to get the code(s)!