Why is My Car Misfiring After Changing Spark Plugs?

You have changed your spark plugs and wires to eliminate misfires. Still, your car engine is somehow misfiring every now and then. Why?

You should know that spark ignition components aren’t the only ones responsible for misfiring. Bad fuel injectors, vacuum leaks, and massive carbon build-up can cause misfiring.

Then, is purchasing new ignition components a complete waste? Of course not! They can truly do some help. But until you fix the other issues causing misfires, new plugs may also get damaged.

What is Misfire?

Engine Activities depend on combustions. The combustion chamber follows a chain that maintains fuel insulation, ignition, and pressure regulation. Whenever this chain gets disrupted, the engine feels like stopping, and other things are pushing it.

The main problem caused by misfiring is decreasing RPM. If you feel the engine is growling or taking too much pressure than it should, either the clutch plate is damaged or the spark plug is misfiring. Avoid driving in such conditions for too long and seek an expert diagnosis.

What are the Other Causes of Misfire?

Changing spark plugs and coils can only help to reduce engine misfire when the ignition system is at fault. So, when you face several half combusts while driving with new plugs, don’t get disappointed. Try to look for other possible causes and their solutions.

To help you out in this matter, I am marking most of the reasons. You can match them with the DTC Misfire Code P0 series for making accurate decisions.

Carbon Build Ups (P030X)

The deposition of carbons on the surface area because of combustion is pointed to as Carbon Build Up. It creates blockages, unignited fuel despite required sparkling, pre-ignitions, and knocks.

How It Harms

Carbon deposits grow slowly. But they can overheat the cylinders easily. They force the engine to consume more fuel. By this, the synchronization of the ignition system gets disrupted.

How to Prevent

To prevent carbon build up from growing, you must use quality fuel. Also while doing maintenance, don’t forget to clean the areas where carbon deposit is possible, such as cylinders, spark plugs, mufflers, etc.

Vacuum Leakage (P0300)

Insulation of extra air in the combustion chambers is called Vacuum leakage

How It Harms

Any leak in the vacuum components can change the percentage of air in the air-fuel mixture. This kind of fuel composition can’t create the pressure pistons needed to keep the engine running. As a result, misfiring happens occasionally.

How to Prevent

You can purchase a sealant and fix the leaks by yourself after detecting the possible leaking areas. But the best alternative here is taking your car to a garage that might cost a handsome amount.

Bad Fuel Injector (P0171/P0172)

The job of a fuel injector is to spray an air-fuel mixture in a specific chamber with high pressure. It needs to maintain the 14.7:1 ratio of the mixture. When carbon covers any section of the injector or the mechanism loses smoothness, it sprays an unusual amount of fuel.

How It Harms

Damaged fuel injectors mostly cause trouble by changing the amount of spraying fuel at a time. It can either cause misfire from lack of power in the chamber or pre-ignition from extra fuel presence. Both issues can break the normal flow of work in your car’s engine.

How to Prevent

There are two ways to fix clogged fuel injectors.

• Use a fuel injector cleaner with the fuel if the injectors are attacked by carbon existences.
• The rubbers, springs, and closures can lose their elasticity or smoothness. That is why spraying can be inconsistent or the fuel might leak anywhere. You can solve this problem by changing those specific parts or purchasing a new injector.

Low Fuel Pressure (P0313)

Injection-based fuel supply to the engine can trouble you for several reasons. It can be either pumping less or bad sensing. In any case, pumping fails to put the required amount of pressure that causes energy drop in the engine.

How It Harms

The fuel circulation system contains several components. Fuel injector is also one of them. But it has different reasons to cause P0171-P0172. Let’s see what causes P0313.

• The pumping capacity should be ≈1.5liters/minute. The pump can fail to touch the margin because of electrical issues or jamming.
• The fuel pressure sensor mounted on the rail can sense the wrong range of pressure and make the regulator add or remove a huge amount of pressure.

How to Prevent

Fixing the wires powering pumps can be the primary step here. You should also check the fuel rails and pipes to identify any block or leak. And, finally, check the sensors by using elsewhere. You need to replace rails and regulators if they are the ones causing trouble.

Exhaust System Failure (P0300)

Exhaust system failures specially indicate exhaust manifold’s leakage or backfiring. The issue is the rarest cause behind P0300 occurrence.

How It Harms

The backfiring or leak in exhaust parts makes the O2 sensors feel the need of adding more fuel to the cylinders. It reduces the mileage, makes engine shaking, and mistimed combustion. Firing at the wrong time, however, can result in P0300 by manifold.

How to Prevent

The troubleshooting here is almost the same as some other issues’ fix mentioned above. You have to find out the leaking area and cover them as firmly as possible. But the only easy solution is changing the manifold gasket if your manifold is backfiring.

Final Thoughts

Nowadays, most cars have software to maintain every section together. So, any unusual activities can be detected by the software.

Features like check engine light, SRS, consistent low fuel light, and other indicators on the dashboard specify the problem to the driver, which makes troubleshooting pretty easy. You can find out the key reasons behind excessive or less firing in the combustion chambers by following thrown codes.