Monthly Archives: June 2018

How To Test And Change Ignition Coil

Today’s topic is how to test and change ignition coil. An ignition coil is responsible for providing spark to the spark plug. Without the ignition coil, the spark plug will not be able ignite the fuel that is sprayed into the engine. A faulty ignition coil will cause an engine to misfire which will ultimately result in a loss of performance. Sometime, one or more faulty ignition coil is enough to prevent the vehicle from starting. A faulty ignition coil will trigger a P0300, P0301 P0302, and P0303, P0304 and so on. Moreover, it also depends which ignition coil has failed. Some of the common sign of a faulty ignition coil are:  rough idle, difficult to start, misfire, random misfire, hesitation, loss of power and no start.

Here are some ways to test if you have a faulty ignition coil. First, conduct a power balance test. With the engine running, simply disconnect one ignition coil at a time. A good ignition coil will result in a decrease in rpm. That means the ignition coil is function and that coil should not be replaced. Continue to conduct the power balance until there is no change when disconnecting the ignition coil. When there is no change that means that ignition coil on the cylinder it was disconnected is faulty. In addition, you can also use a test light to test for spark. Remove an ignition coil and connect the test light to battery negative. With the engine running, point the test light close to the boot of the ignition coil. If the ignition coil is good; there should be spark.

Next, you will need an OBD 2 scan tool to confirm the ignition coil is faulty. Locate the OBD 2 port and connect the scan tool. Next, press the read code button. The scan tool will give you a few codes if the check engine light is on. For example: Let’s say you disconnected cylinder number two and there is no change in rpm and let’s say the scan tool detected fault in cylinder number two or P0302. That means the ignition coil is faulty on that cylinder. When replacing an ignition coil, try to stick with OEM brands and not aftermarket parts. Usually, an aftermarket part will not last as long as OEM brands and it may not provide the full spark and spark plug needs.