Ford Fiesta Miss-Firing

Problem My Ford Fiesta Zetec is now miss-firing particularly when I am just idling along and decide to accelerate quickly.
This has been going on for some months now as I have since changed the spark
plugs, distribution leads and had the engine cleaned out just in case the cause was contaminated fuel. Unfortunately these changes have had no affect what so ever and left me none the wiser I hasten to add.
Can anyone out there offer any advice?
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Problem My Ford Fiesta Zetec is now miss-firing particularly when I am just idling along and decide to accelerate quickly.
This has been going on for some months now as I have since changed the spark plugs, distribution leads and had the engine cleaned out just in case the cause was contaminated fuel. Unfortunately these changes have had no affect what so ever and left me none the wiser I hasten to add.
Can anyone out there offer any advice?
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You could try finishing the tune-up with a new cap and rotor. That will help to ensure you are getting good spark.
You should also do a compression test to ensure all cylinders are getting roughly equal compression. Preferably you should do a compression test first as it may let you know if you have any 'serious' problems like worn/broken rings, burned/bent valves or worn valve seats.
If you get a misfire at idle or a rough idle you could try unplugging one spark plug wire at a time. Each wire you unplug should drop the engine RPM the same amount. If when you unplug one of them the RPM cahnges less than the others that will tell you that cylinder has a problem.
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