Subaru Ignition Coil Problems

Is your Subaru behaving more like a stubborn mule than the nimble road runner you fell in love with? Bucking, misfiring, or even refusing to start at all could be signs of Subaru ignition coil problems. 

As an essential part of your vehicle’s engine, the ignition coil is responsible for converting low-voltage power into enough wattage to kickstart the spark plugs and get your car moving. When it falters, so does your ride.

And of course, you won’t let yourself encounter such issues, right? However, sometimes electrical problems are unavoidable. But don’t be hopeless, as we’re here with you. Let’s delve deeper into understanding the intricacies of the Subaru Ignition Coil Problems that could potentially interfere with your smooth rides.

Related: Warning Signs of a Bad Ignition Coil: What Every Driver Needs to Know

Subaru Ignition Coil Problems

Subaru Ignition Coil

Cracking the mystery around Subaru Ignition Coil Problems doesn’t demand you be a pro mechanic. It’s all about awareness and keen observation. 

Whether it’s frequent misfires, rough idling, or a noticeable lack of engine power, all suggest that your ignition coil could be staging a revolt under your hood. This will be more evident if you look at the common issues discussed below. 

Ignition Coils Failure in Cold Temperature

Many people have reported Subaru Forester ignition coil problems related to the failure of the ignition coils. The vehicle struggles to start or doesn’t start at all when the temperature drops below 10F. A similar starting issue was identified in 2004, which was traced back to a faulty ignition coil. 

Despite the recurrence of the problem in 2005, the dealer’s service department failed to identify or articulate the issue. Nevertheless, as more and more people encountered this problem, a detailed investigation was undertaken. The analysis confirmed that failure of the ignition coil was indeed at the heart of this recurring issue with Subaru Foresters.

In 2006, Subaru released a service bulletin acknowledging the ignition coil problem in some of their Forester models. It was recognized that when the temperature dropped below certain levels, there was an increased chance of ignition coil failure. 

However, even with this acknowledgment from the manufacturer, many Forester owners still struggled to get their problems fixed under warranty. One common complaint among these affected owners pertains to poor engine performance and misfiring once the car is started after tough resilience during cold weather. 

In extreme cases, smoke can be seen coming from underneath the hood due to faulty spark plugs, indirectly caused by defective ignition coils. Fast forward to modern-day 2022, it’s disheartening but not surprising that Subaru Foresters are still battling with similar incidents relating to ignition coil failures. 

Multiple reports have flooded in detailing scenarios where people were left stranded on winter roadsides with no way for their vehicles to turn over or start all thanks to failed ignition coils.

Related: Cooling Your Ignition Coils: Maintenance Guide For High-Performance Engines

Misfiring Engine

Ignition coil issues, particularly misfiring, are not uncommon in motor vehicles. However, Subaru Outback ignition coil problems are mostly centered on misfiring in the engine which has panicked numerous owners. 

A large number of these owners have specifically reported misfires occurring in cylinder 3. Attempts to rectify the issue by replacing the plugs did not yield positive results. Interestingly, the issue persisted even after the ignition coil was replaced.

One owner’s account offered an insightful observation: after swapping spark plug wires 1 and 3, he noticed that the misfire had moved to cylinder 1. This indicated that spark plug wire 3 was defective. 

Fortunately, replacing these wires resolved the misfire issue. However, another problem surfaced soon after the vehicle began stalling when it reached operating temperature. 

The pattern observed was that once warmed up, the vehicle would run roughly before stalling and refusing to restart until it had cooled down somewhat. This behavior would typically occur approximately 15 minutes into driving, but would then persist.

How to Troubleshoot A Bad Ignition Coil In Subaru Forester?

Performing a test on the ignition coil of a Subaru is not complex at all it’s quite uncomplicated. The ensuing guidelines are particularly for the Subaru Forester model. The procedure is more or less the same for most Subaru vehicles, however, it’s recommended to conduct an online search to confirm the resistance specifications. 

During your ignition coil assessment, it would be wise to also examine the condition of your spark plugs and wires. A digital multimeter will be your sole tool required for measuring resistance. Here’s how you do it: 

  • First, connect a scan tool to your Forester’s OBD2 port. This will allow you to read the error code; for instance, P0303 would mean that cylinder number 3 is misfiring. To avoid any burns, ensure the engine is cool before proceeding.
  • Next, remove the ignition coil from cylinder 3 (or whichever cylinder is misfiring) and switch it with another one (let’s say from cylinder 2). Be careful not to swap the spark plug wires connectors, only exchange the ignition coils. Disconnect the electrical connectors before swapping and reconnecting them afterward.
  • Once this is done, start your Forester again and use your scan tool to read any new error codes. If you now see an error code P0302 (which implies that cylinder number 2 is misfiring) instead of P0303 and there are no longer any misfires on cylinder number 3, this confirms that your ignition coil is defective and needs replacing.

However, this approach only applies to vehicles equipped with coil-on-plug (COP) type ignition coils; it will not work on those with coil packs.

Ignition Coil Replacement Process in Subaru

Switching out the ignition coil on your Subaru Forester is a straightforward task, all you require for this are a socket or wrench set and a flathead screwdriver. The initial step is to secure a new ignition coil. For optimal compatibility and durability with your Subaru, an OEM part is recommended. 

Once you’ve parked your Forester, here’s the procedure to follow for replacing its ignition coil: Open up the hood and disconnect the battery. If there’s an engine cover present, take it off. 

You’ll find the ignition coil positioned atop the engine, centrally located, with four spark plug wires attached to it. For ease of reinstallation, label each spark plug wire using a white marker; this ensures they are reconnected correctly after installing the new ignition coil. 

Detach all spark plug wires from their current position on the ignition coil. The ignition coil is held in place by either two or three bolts – unscrew all of them to remove it. 

Place your new ignition coil into position and secure it using the same bolts you recently removed. Reconnect all spark plug wires according to their respective numbers marked earlier. 

If there was an engine cover initially, put it back onto its rightful place on top of the engine. Reconnect your battery and start up your vehicle to check if any previous issues still exist (You can refer to this list for symptoms of a malfunctioning ignition coil).

Final Words

Subaru ignition coil problems are not uncommon and can significantly impact the performance and efficiency of your vehicle. Always err on the side of caution when faced with potential ignition coil problems; early detection can save you from costly repairs in the future. 

Consult with a qualified mechanic or a Subaru specialist if you suspect any ignition coil-related issues. Remember, taking care of your car is an investment, and it’s always better to address small problems before they escalate into more significant issues.

Leave a Comment