I recently had the opportunity to diagnose my friend’s troubled car which is a 2007 Ford Focus 1.8L gasoline engine. I am actually not a professional mechanic though I think I have enough knowledge about car repairs and maintenance tasks.
His car is having a hard time starting and sometimes stalling. When it runs, it has low power, and when it is in idle, the engine vibrates violently and is jerking. Not to mention that his dash shows engine warning light and a malfunctioning fuel gauge.
So I did my research first, did some notable diagnosis on its ignition system, battery and fuel system. Sadly, much of the results turned negative. That’s when I turned my attention to the spark plug and ignition coil.
And boy the culprit is a bad ignition coil. Before I discuss how to diagnose a faulty ignition coil, let me first give you what is an ignition coil and some of its notable symptoms when it starts malfunctioning.
What is an Ignition Coil?
According to WikiPedia, an ignition coil is an important part in car’s ignition system of a petrol-based engine. This means in a spark-ignition engine. It is constructed of two sets of coils wound around an iron core. Today’s modern engines are now using distributorless system, wherein every cylinder has its own ignition coil.
The main purpose of ignition coil is to convert the low current from your car’s battery into enough power to help ignite fuel and start the engine.
So if your engine has one or more faulty ignition coil, then it will cause a wide range of mechanical and performance issues. So what are the signs of a faulty coil?
Signs of a Bad Ignition Coil
Power Loss
The very first thing that you’ll notice when your coils are failing is power loss. A failing ignition coil will make your engine weak and will not perform as good as usual. Power loss from a bad coil is caused by intermittent sparks which results to poor combustion. If you are having power loss from your car, then you better check the ignition coil first.
Hard Starting and Stalling
A spark-ignition system requires a spark at the right time for the engine to start. A bad coil will not deliver the required voltage to the spark plugs, which results to hard starting issues. Sometimes, most people believe that hard starting is always caused by a bad battery. That is not always the case so you have to understand the health of your battery before you conclude that you need replacement. A failing ignition coil causes hard starting, and for extreme cases, even stalling.
High Fuel Consumption
If you notice that you car consumes more fuel than usual, then you probably have one or more failing ignition coils. It will get more oxygen than usual, and more oxygen means the spark plugs aren’t getting enough power.
A malfunctioning coil will result to wrong data being read by your car’s oxygen sensor. That data will be then forwarded to your ECU which will then send more gas to the chamber than the usual required amount. This is because the oxygen sensors are getting higher volume of air, which the ECU will have to compensate by sending more fuel to the chamber to get proper combustion process.
Check Engine Light On
Modern vehicles are very smart and will outright tell you if you have issues with your car. One reason why check engine light pops up is because of a failing ignition coil. Get yourself a quality OBD scanner and see what the engine light is all about and try to fix it yourself.
Backfiring
When you notice your car makes a loud bang sound when driving, then you are most likely suffering from engine backfires. This issue is caused when unused fuel in the combustion cylinders suddenly explodes, which emits black smoke from the exhaust. And yes, one of the reasons why backfires occur is a failing ignition coil.
Engine Misfires
Does your car misfires when you are accelerating? If yes, then your vehicle’s cylinders are misfiring. And yes, one of the causes of engine misfires are bad ignition coil. Get your car to your dealer and have it fix immediately if you have this type of issue.
Jerking and Heavy Vibration
As mentioned above, my friend’s car is jerking and vibrating heavily either when accelerating or in idle. If your vehicle hesitate and jerk forward when you step on the gas pedal, then you have issues with your coil. Learn how to diagnose a failing ignition coil and know how to fix the problem yourself. Here’s how!
How to Diagnose and Fix a Bad Ignition Coil?
If you have done your research and closed out all the possible culprits and still your car has starting issues or is jerking and has low power, then it is time to check your ignition coils.
Most cars have four ignition coils (this varies to the number of cylinders your engine have) and is found on top of your engine where your spark plugs sits.
To start your diagnosis, you need to start your engine and check each coil one by one. Coils have bolts which are commonly size 10mm. Unbolt it and pull the coil up while the engine is running.
If the engine reacts while you are pulling the coil, then that ignition coil is still functioning and good. In contrary, if the engine doesn’t react and continues to run while you slowly pulling the coil up, then that ignition coil is already bad and needs replacement.
If you spot which coil is faulty, reach your vehicle manual and check for the correct type of ignition coil for your engine. Then go to your nearest dealer or auto shops and get a brand new OEM coil for your engine.
Just unplug it from its wiring connection to remove the bad ignition coil. Plug the wire and install the new ignition coil back in, and you are done!
Conclusion
Most people don’t know what to do once they experience issues with their cars, especially when it comes to jerking, vibration, hard starting and stalling. They often go straight to their local auto repair shops and spends hundreds to thousands of dollars.
Now that you know how to diagnose and repair bad ignition coil, you can repair your car yourself and save money and time!
If you have learned something from this post, take time to comment below and please follow my Youtube page – Noah’s Garage. Below is my video regarding this same topic. The language is in Tagalog, though I completely explained everything in this post, so please understand! hehe
