Unplug one injectors at a time when the cars is running. The car should stumble when you unplug the injector, but when you unplug the cylinder that is miss firing you shouldn't notice much difference in the way it runs. Once you know which cylinder has the miss, pull the plug and swap it to a different cylinder if the miss fallows the plug you have a bad plug replace it with a new one. If the miss stay on the same cylinder as before regardless of the plug being changed you might have a bad wire, coil, or injector. Hope this helps.

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