Last Updated: 07.04.2022

Your Ford F150 4.6 L engine needs three things to get its internals working: spark, air, and gas. Without one of these things, your engine will waver and you will not be able to make it uphill.

The spark plugs in your truck are responsible for creating the crucial spark needed to ignite the fuel and gas mixture. If the spark plugs are damaged, you can expect a series of problems like engine misfire, rough idle, slow acceleration, difficulty starting, and poor fuel economy, among others.

At this point, the most ideal thing to do is to change the spark plugs. If you’re wondering how to change spark plugs Ford F150 4.6 L engine, you need to keep reading to learn more.

But first, let’s explain… 

What Are Spark Plugs?

old and new spark plugs

Spark plugs are among the most important parts of your F150 4.6L engine. They’re in charge of generating the much-needed electricity to start your truck.

Each spark plug in your F150 4.6L engine produces a high-voltage electricity jump between two surfaces to create a spark. Then the spark ignites a compressed gas and air mixture in the combustion chamber. 

The generated combustion rotates the truck’s engine components to turn the wheels. But spark plugs wear out, and that’s why they should be replaced when needed. 

Check the Condition of Your Engine’s Spark Plugs

Spark plugs wear out with everyday use. They are part of your truck’s maintenance and that’s why it is important to check their condition.

We, however, suggest that you check the condition of your spark plugs as recommended by the truck’s manufacturer. In most cases, it is recommended to replace spark plugs every 12 to 24 months or every 15,000 to 30,000 miles. The high-performance types are a cut above the rest and could operate up to 100,000 miles before a replacement is necessary.

You’ve probably wondered how you can tell your Ford F150 needs new spark plugs. Let’s talk about that next.

Signs of Bad or Fouled Spark Plugs

You will know that it’s time you learned how to change spark plugs Ford F150 4.6 L engine when you start seeing the telltale signs of fouled or bad spark plugs.

You can know what is going on with your engine when you take a look at the electrodes and porcelain of your spark plugs. Several things can foul a spark plug. 

The first one is a rich fuel mixture, which will show up on the electrodes and porcelain as a gray to a matte black finish. This is usually due to too much fuel in the cylinders. The excess carbon takes residence on the hot parts of your plugs. 

The second one is an engine oil leak. The oil on your spark plugs will create a black finish or a shiny black finish in some rare cases. The black coating will be blotchy as well as inconsistent.

The third one is a coolant leak. A leaking intake manifold gasket or head gasket could allow the coolant to get to the combustion chamber. The coolant can stick to your plugs and cause them to foul or go bad. This will be indicated by a gray-ashy finish.

Now you know the potential causes of your plugs going bad, let’s dive into the various signs of fouled spark plugs in your truck. 

Engine Misfire

This occurs when there’s an interruption with the fuel charge in any of the cylinders, causing ignition failure.

If your truck’s engine misfires at specific conditions and not all the time, then that’s an intermittent misfire. The condition generally results from a lack of spark mostly due to an excessively lean or rich fuel charge. The PCM is responsible for detecting a misfiring cylinder and you get an alert when the check engine light goes on.

A misfiring could make your truck’s engine shake as well as run unevenly. This is what you would notice when accelerating from a stop or at idle. 

Slow Acceleration

If the plugs in your truck are fouled, your Ford F150 4.6l engine will struggle to generate the much-needed speeds when you step on the accelerator pedal. This is one of the solid reasons you need to change the spark plugs.

Rough Idle

Does your Ford F150 do a rough idle? If that’s the case, don’t ignore the condition. Rough idle is a sign that your engine isn’t running as smoothly as it should. This can lead to poor fuel economy. Fouled spark plugs are among the top culprits.

Hard Start

You are likely to experience a hard start when you’ve got fouled plugs in your engine. Extra energy may be needed to get the truck started.

How to Change Spark Plugs Ford F150 4.6 L Engine

What You Will Need

  • 9/16 spark plug socket
  • 1/2-inch ratchet with an adapter

Step-By-Step Instructions

Step 1: Removing the Spark Plugs

removing the spark plugs

The stock spark plugs tend to break in the cylinder head when you go to replace them. This is so due to the design of the extended tip of plugs.

Carbon and soot usually accumulate between the cylinder head and the tip of the plug during normal operation, creating a tight bond. So, when you try and loosen the plug, the nut, and top section of the porcelain can break off. With that said, we will go ahead and get those fouled spark plugs out.

removing the coils

The process starts by removing the coil packs one by one to have unrestricted access to the spark plugs. It is also good to check the condition of the coils. Once the coils are out blow the spark plug well to get grime, leaves, and debris out.

You need a 9/16 spark plug socket and a long extension to create more room. A lot of times you have to use a 1/2-inch ratchet with an adapter to get the additional turning torque. Start by cracking the plug loose and go less than half a turn. In some cases, you may hear some squawking.

shoot penetrating oil or tune-up cleaner

Then shoot some penetrating oil or tune-up cleaner down the hole and allow it to soak for 30 minutes.

remove the spark plug

The oil will help loosen the carbon buildup, making it easier for you to remove the plugs without breaking them. If a spark plug breaks off in the cylinder, you will have to seek the services of a mechanic to have the broken plug removed. 

Step 2: Replacing the Spark Plugs

replacing the spark plugs

For replacement, we prefer using updated one-piece spark plugs instead of two-piece versions.

This will eliminate any problems in the future when you want to replace the plugs again. Not to mention that the updated one-piece versions are double platinum. So, they’ve got a significantly longer service life.

To make sure that the new plugs will not get stuck during the next tune-up, we will use a high-temperature anti-seize lubricant. We recommend applying the anti-seize to the threads as well as the tip of each spark plug.

install the new spark plug

Blow the spark plug wells one more time to make sure that you get rid of all the dirt and fluid before installing the new plugs. Put the new spark plug into the well by hand to avoid cross-threading. Then use a 3/8 ratchet and tighten the plug down until it stops. Add the necessary torque to prevent the plugs from coming loose. Do the same with the other new spark plugs.

reinstall the coil

Check the condition of the coils and make sure that they are nice and clean. They shouldn’t have any coolant, oil, debris, or grime on them. Lubricate the coils with a small amount of dielectric grease and then reinstall them.

It is also a very good idea to deal with one cylinder at a time to avoid any problems.


Will the Ford F150 4.6L engine spark plugs break of?

The stock two-piece version of spark plugs is known to break off into two parts when trying to remove plugs. A broken spark plug in your engine is a big problem, which could easily lead to high repair bills.

What can I do to get the spark plugs out without breaking into two?

After removing the coil and cleaning the spark plug well, we recommend shooting penetrating oil into the plug and allowing it to soak for at least half an hour before trying to remove the plug. Make sure you coat the new plugs with an anti-seize for an easy tune-up in the future.

Can I remove broken spark plugs from my engine?

If a plug breaks into two when trying to remove it, we recommend you tow the truck to a mechanic shop and have them remove the broken piece at a fee. It isn’t an easy job for a DIY and you probably don’t have the necessary tools.

The Bottom Line

Your Ford F150 4.6l engine spark plugs aren’t designed to last forever. They will eventually go bad or get fouled, especially when exposed to rich fuel mixture, coolant leak, or engine oil leak. So, you must know how to change them. Your skills will come in handy when you experience engine misfire, rough idle, and slow acceleration among other things.