If your 2005 Ford Soul has a rough idle, hesitates when you press the gas, or the Check Engine Light is flashing, a misfire is likely happening. One of the most common causes of a misfire is the spark plug gap. The gap needs to be just right. Get it wrong, and the engine won't run properly.

This is a straightforward fix. But you need to know what to look for and what the exact specification is. Right in our main article on signs of a misfire in the 2005 Ford Soul, we break down the symptoms. Here, we will focus on how the gap specifically causes those issues and what you can do about it.

What exactly is a misfire and how does spark plug gap cause it?

A misfire means the fuel in one of your cylinders didn't ignite. Think of a campfire. If the spark is too small or too far away, the wood won't catch fire. The spark plug needs a precise distance to jump the gap. This creates the spark. If the gap is too narrow, the spark is weak. If the gap is too wide, the spark might not happen at all. Either way, your 2005 Ford Soul will misfire.

How do I know if my 2005 Ford Soul has a misfire from the spark plug gap?

The symptoms are usually obvious. You don't need a mechanic to know something is wrong.

Rough idle and shaking

When you are stopped at a red light, the car may shake. The vibration will be steady. If the gap is off on one cylinder, the engine will run unevenly. You will feel it in the seat and the steering wheel.

Check Engine Light flashing

A steady light is one thing. A flashing light means a serious misfire. This is bad. It means unburned fuel is going into the exhaust. This can damage the catalytic converter. If you see a flashing light, check the spark plug gap first.

Poor acceleration and hesitation

You step on the gas. The car stutters. It feels like it is holding back. This hesitation is a classic sign that the spark isn't strong enough to burn the fuel quickly. A properly gapped spark plug gives you instant power.

Is it the spark plug gap or something else?

Spark plug gap is the most likely cause of misfire symptoms on an older engine like the 2005 Ford Soul. But other parts can cause similar problems. Bad ignition coils, vacuum leaks, or dirty fuel injectors also cause misfires.

The good news is checking the gap is free. Start there. If the gap is correct but the car still misfires, move on to the coils. Running the wrong gap for a long time can damage the coils. Read more about how the incorrect spark plug gap leads to ignition coil failure so you know what to look for.

What is the correct spark plug gap for a 2005 Ford Soul?

This is the most important number. Do not guess. Do not trust that the spark plugs are pre-gapped. The correct gap depends on your engine size. For most 2005 Ford Soul models, the factory gap is around 0.050 to 0.054 inches. But you must verify this for your specific engine.

If you want the exact factory gap for your engine size, check the specific gap specification for the 2005 Ford Soul. Always use the manufacturer spec for NGK or Motorcraft plugs.

How to check and fix the spark plug gap on your 2005 Ford Soul

You can do this yourself with a simple tool. You need a gap gauge or a feeler gauge. Here is the process:

  • Remove the spark plug carefully. Do not drop it. Dropping it can damage the insulator.
  • Slide the gap gauge between the center electrode and the ground electrode. The gauge should fit with a slight drag.
  • If the gap is too wide, gently press the ground electrode against a hard surface to close it.
  • If the gap is too narrow, use the notch on the gap tool to pry the ground electrode open slightly.
  • Never pry against the center electrode. This breaks the plug.

Common mistakes people make when gapping spark plugs

Avoid these errors:

  • Using a cheap flat gauge. These are not accurate for modern spark plugs. Use a wire-loop gauge or a coin-style gap tool.
  • Forcing the gap tool. You should measure, not pry hard. If you force it, you change the gap while measuring it.
  • Dropping the spark plug. Even a short drop on concrete can crack the insulator. A cracked plug will misfire every time.
  • Assuming they are pre-gapped. Always check the gap. Even brand new NGK plugs can be off by a few thousandths.

What to do after you fix the gap

Put the spark plugs back in. Tighten them to the correct torque. Do not overtighten. Start the engine. If the rough idle or hesitation is gone, you fixed it.

If the misfire comes back after a few days, check the gap again. It might be closing up, which indicates a deeper issue. If the misfire is still there, you likely have a bad ignition coil. Check for spark at each plug wire. No spark means the coil is dead.

This guide was typeset using the Open Sans font for easy reading.