How Do You Check An Ignition Coil Or Fuel Injector?

An ignition coil can be OHM checked with a meter to see if it is out of range or if it has a completely open circuit. But what if the car seems to run fine and a misfire code is directing you to a particular cylinder? For instance if you have a code for * P0301 (#1 misfire code) but the engine seems to be running OK, below is a low tech method for testing the coil without any special tools. This method works well for ignition coils or fuel injectors that may have an intermittent problem. Also it works best with ignition coils and injectors that are easily accessible. Obviously it's best to check the basics first like a visual inspection to see if engine oil may be shorting a connection or if there is evidence of tracking of the spark arcing to the engine. Sometimes after an engine is cleaned water can go into the spark plug recess and short the connection to the plug as well. The simple low tech method is assuming the spark plugs and wires are good and there is still a misfire code ...  more