Common Ignition Problems

An ignition issue can be caused by a faulty or failing ignition coil, spark plug, or spark plug wire set. These critical components of your ignition system keep your engine running smoothly. If they have a problem, you’ll notice a rough ride, engine misfires, and possibly decreased gas mileage, along with in most cars, a Check Engine Light (CEL) for a misfire.

Often times, replacing the failed or failing part will correct this issue.

Ignition coils and wire sets are fairly straightforward to replace. However, some applications will require removal of major components such as the upper intake plenum manifold. Reference a repair guide for more specific information for your vehicle. We highlight how to properly test your ignition coils, or troubleshoot problems here.

Spark plugs may require a bit more attention on some vehicles. Some can be very easy to get to and replace, where other ones are a long, complex job depending on their location. We have a guide on replacing spark plugs. Some spark plugs need to be gapped and have anti-seize applied before installing and some do not. Check the spark plug manufacturer’s requirements.

Spark plugs should always be installed with a spark plug socket and tightened to the proper torque. If you need a torque wrench, borrow it from AutoZone through the Loan-A-Tool program.

Any modern ignition system that doesn’t use a distributor has to have a method at which to determine the precise moment to fire the ignition coils. To do this, a crank position sensor is used, which is essentially a magnetic trigger. At the precise moment in revolution, the sensor picks up a trigger point in the rotating crank, and sends signal. When this sensor fails, this signal is lost. Sometimes, it the part fails completely and you have either a dead vehicle on the road, or a no-start situation. Other times, the problem can be intermittent, leading to misfires, or stalling issues. In most cases, when this occurs, the vehicles engine computer will pick up a code for crank position sensors.

Like it’s cousin, the crank position sensor, a cam position sensor does the same thing on the engine’s camshafts, or multiple camshafts. These devices read the position of the cam in respect to ignition timing, to either advance (make the spark come earlier) or retard (make the spark come later) in the stroke.

When a cam position sensor goes awry, you can experience much of the same issues – misfires, lack of power, poor gas mileage, or a no-run / no-start situation. Like most sensors, it’s also picked up by the vehicles engine computer, so if there’s a fault, an engine code will pick it up.

Very similar to a crank position sensor, in distributor-style ignition systems that do not use breaker points, each distributor has a pick-up coil, or hall effect sensor (same thing) that reads a cog wheel inside the distributor to accurately pick up and tell the precise moment when to send a signal to the coil to fire.

When a pick up coil goes out, you generally have a no-start situation. Many people often think this is the ignition coil, but often times, the pick-up coil is the culprit. Changing these coils can be difficult, because often, the distributor must be completely removed to gain access to it.

Many vehicles made in the last 10 years no longer use a proper Ignition Module, and instead house its function either in each individual coil, or in the vehicles onboard computer. Ignition Modules were the standard for many electronic ignition systems from the late 70’s all the way through the early 2000’s. Many foreign vehicles refer to the unit as a power output stage control, or ignition control unit, but they are all the same thing.

These devices help process the signal from a crank position sensor or pick-up coil in a distributor system and distribute the signal of when the coil should fire. When they go out, you can have a misfire, coil packs not functioning properly, or a no-run / no-start situation.