How do I cure Fiesta misfire?

My wife's Fiesta was slightly lagging a bit on take off so I gave the car a service, the usual like oil air filter plugs. After installing the plugs the car was misfiring. So I have done a full check on the the leads put new leads in, still happening so I changed the coil. Still happening and then to add to it the radio and trip computer keep resetting on startup. The mis fire is still there. Also i checked the flow of the injectors they are all fine. I did a compression test and that was 14 across all 4 cylinders and holding at that too. I'm lost, please help.
So did you try isolating each cylinder? i.e remove one lead at a time and see if the engine note changes. Also try by releasing one injector at a time, again to see if the engine note changes ( although the flow may be okay the Injector may be faulty).

Other than that it may be one of the sensors. i.e MAP sensor, IAT (intake air temp), HO2S sensor (sometimes called a Lambda sensor), ECT (engine coolant temp sensor).

We assume that you have checked for all air/vacuum leaks? You may have to have a diagnostic carried out if all else fails.
Answered by Alan Ross on

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