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.

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1 answer
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)!