6 Reasons Your Check Engine Light Flashes and Your Car Shakes
For the average driver, there are few situations more stressful than suddenly noticing that your car has started shaking violently while your new check engine light is on. Learn about the various causes of vehicle shaking accompanied by a flashing check engine light and whether it is safe to continue driving.
Check for a Flashing vs. Constantly Lit Engine Light
In general, there are two different types of check engine lights, the first being a constant-on check engine light. The second type is one that flashes repeatedly at a set pace.
In most cases, the latter of these two types of engine check lights indicates that a more serious problem is currently underway. If the Check Engine Light is on, it usually indicates that diagnostic trouble codes have been logged and stored (or not), regardless of whether they are currently active.
A flashing Check Engine Light is usually intended to convey an important message to the driver. This message is usually regarding a current misfire detected in one or more specific cylinders.
Here are some of the most common causes of cylinder misfires:
1) Bad/damaged/filthy spark plugs
Your engine’s spark plugs are responsible for providing each cylinder with the spark it needs to start combustion. Over time, spark plugs can become fouled or improperly gapped, making them difficult or unable to ignite.
This causes a misfire, which can only be fixed with proper maintenance. Checking the condition of your spark plugs (and replacing them if necessary) can help prevent future misfires.
2) Damaged ignition coil/spark plug wires
Ignition power is delivered to the cylinder’s spark plugs via a special spark plug cable or a special ignition coil (for engines with ignition coil ignition systems).
Over time, and when exposed to the heat generated by the engine, the insulating outer casing of these components can become brittle and crack, causing ignition power to reach the ground prematurely.
3) Damaged/corrosive distributor cap or faulty ignition coil
Another possible cause of active misfires is a partial failure of the engine’s distributor cap or ignition coil. Many older internal combustion engines used such devices to time the spark delivery to each cylinder. Unfortunately, distributor caps were prone to cracking and corrosion, and coils frequently suffered from heat-related failures.
4) Fuel Delivery Issues
Another common cause of misfires is one or more faulty fuel injectors. An injector can fail mechanically or electrically, causing fuel not to be metered into the corresponding cylinder. This results in no combustion catalyst and robs the cylinder of power. This causes a clearly noticeable shudder that can be felt immediately.
5) Compression Loss
Somewhat less common, misfires can be caused by a loss of compression in one or more cylinders. This is common in high mileage engines and older models.
Compression loss can be caused by damaged piston rings, damaged pistons, or valve issues. Severe head gasket damage can also cause sudden compression loss.
6) Emissions-Related Misfires
Faulty or inadequate exhaust emission control devices can also be the cause of persistent misfires in one or more cylinders of an engine. This most commonly occurs when the EGR valve is stuck in the open position.
If your car’s check engine light is currently flashing and accompanied by a noticeable shudder, it’s best not to drive any further than necessary to reach a safe destination. Unlike a “Service Engine Soon” light, this can have serious consequences.
As mentioned above, this type of symptom is almost always associated with an engine misfire, or partial/complete loss of combustion in one or more cylinders.
Either way, the root cause of your vehicle’s misfire should be thoroughly diagnosed and addressed as soon as possible. This will prevent further issues from occurring, which often cost quite a bit to repair.
