Ignition Module Problems

by Dan Ferrell
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jeffk: Flickr.com

A failing ignition control module can be a real headache at times. It can produce a wide range of engine performance problems, including preventing the engine from starting or stalling the engine as you speed down the road, just to let you resume your driving a few minutes later, as if nothing had happened. Before any of these symptoms send you troubleshooting components or systems unrelated to the root cause of the problem, there are some other things you should know when dealing with a possible bad ignition module on your vehicle.


The ignition control module on your car operates as a switch to turn the primary current produced by the ignition coil on and off. The module accomplishes this through a series of very small and sensitive electronic components inside the sealed plastic housing of the control module. The distributor uses this electrical current to ignite the air/fuel mixture in the combustion chamber.


Ignition modules come in more than one configuration and size, depending on your particular car make and model. However, your vehicle service manual may provide instructions on how to test your particular module. For this, you need a 10-megaohm digital multimeter. Most auto parts stores will test the module for you free of charge.


A bad module may pass a troubleshooting test even though one or more electrical components inside is damaged. Tiny transistors, diodes, resistors and other components are very sensitive to heat. And any of these components, near breaking down, may not fail until there is enough heat in the engine compartment. When testing at home, heat up the module by using a heat lamp. Then proceed with the tests as described in your vehicle manual, and compare your results with the specifications provided.


Installing a new ignition module is a simple process. Depending on your vehicle model, the module may be mounted inside the engine compartment, near the engine, or inside the distributor. Remove the distributor cap if necessary. Then unplug the module electrical connector and unscrew the unit. Install the new one in place, plug the electrical connector and replace the distributor cap, if necessary.


Some ignition modules require a layer of silicon grease during installation. The grease protects the mating surface of the module from the heat produced during engine operation. When replacing the module, check with your auto parts provider whether you need to apply this grease to your particular unit. Otherwise the new module will fail within a few weeks of replacement.

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