What Is Engine Timing?

Imagine watching a movie where the audio wasn’t perfectly timed to the video. It’s the exact type of film you like too, and yet it’s hard to appreciate the story, acting, or anything else because of the audio’s one-second delay.

In a way, your vehicle’s engine is a lot like that. If the timing of any of your engine’s parts is off by just one second, your entire engine’s performance is compromised.

What Is Engine Timing?

Have you ever wondered how your engine runs so seamlessly even with so many moving parts? Well, it all comes down to engine timing.

Whenever you drive your vehicle, several parts of your engine have to constantly move in perfect harmony in order to keep your vehicle running. They follow a strict timing system that makes sure not even a single part falls behind.

There are two different types of timing in an engine: cam timing and ignition timing.

Cam Timing

The easiest way to understand cam timing is to think of the heaviest parts of your engine and how they all repeatedly move in perfect harmony. Thanks to cam timing, these parts all move in perfect synchronization to make way for your spark plugs to ignite the air-fuel mixture in your vehicle’s combustion chambers.

When your pistons move up and down, they have to be perfectly timed with the opening and closing of your valves. Of course, this movement also relies on the rotation of your engine’s crankshaft, which is linked to the camshaft by an engine timing belt or chain.

If your vehicle’s cam timing is off, your pistons and valves will end up hitting each other, and your engine probably won’t start.

Ignition Timing

When you start your vehicle, your spark plugs send a bolt of electricity that ignites the fuel in your combustion chambers, sending your pistons in motion and your vehicle moving.

The spark is delivered before the piston reaches top dead center and its timing is measured in degrees of crankshaft rotation. Since fuel only burns at a certain rate, as the engine picks up speed when it’s not pulling a heavy load, the spark happens earlier to get the most benefit from the combustion event.

Thus, older engines had a vacuum timing advance and a centrifugal timing advance built into the distributor. Newer engines without distributors depend on the engine controller for timing control. With coil-on-plug engines, each cylinder’s timing can be controlled separately if need be according to knock sensor input.

Ignition timing plays an important role in making sure your engine’s spark plug doesn’t fire too late or too soon. If the ignition timing is just a little bit off, you’ll likely notice a decline in engine performance.

How Does Engine Timing Work?

To better understand how engine timing works, it’s important to understand the four events your engine repeatedly cycles through to keep running.

Most modern vehicles have a combustion engine whose pistons have to complete a four-stroke cycle that continuously repeats for as long as the engine is running. These four strokes are the following:

Intake Stroke

The piston’s movement from the top dead center (TDC) to the bottom dead center (BDC) creates a vacuum that draws the air-fuel mixture into the engine through the open intake valve.

Compression Stroke

The intake valve closes, and the piston moves from the BDC to the TDC and compresses the air-fuel mixture in the combustion chamber. Before this stroke ends, the spark plug ignites the air-fuel mixture.

Power Stroke

The ignition pushes the piston down and rotates the crankshaft, powering the vehicle to move.

Exhaust Stroke

The piston moves up from the BDC to the TDC, and as the crankshaft keeps moving, the exhaust valve opens to release burnt fuel from the cylinder.

Each step in this cycle relies on the proper timing of your engine. Ignition timing controls when the spark plugs ignite during the compression stroke, while cam timing controls the pistons, valves, and crankshaft in each stroke. A delay in either of these timing systems will disrupt the entire cycle and cause your engine to fail.

How To Tell if Timing Is Off on an Engine

It isn’t always easy to diagnose bad engine timing, but there are some common symptoms you can watch out for.

Signs of Bad Cam Timing

If your engine’s cam timing is off more than a small amount, then your vehicle probably won’t start. On the rare chance that it does, your engine will most likely misfire, make unusual rattling noises, and produce more emissions. In some cases, you might notice your vehicle’s revolutions per minute (RPM) fluctuating too.

If the ignition timing is too early or advanced, hard (kickback) starting and ping/labor knock can happen. If the ignition timing is too late (also referred to as “retarded”), the engine will run sluggish, get poor fuel economy, and can even overheat.

–Richard McCuistian, ASE Certified Master Automobile Technician

Signs of Bad Ignition Timing

If the ignition timing is too early or advanced, hard (kickback) starting and ping/labor knock can happen. If the ignition timing is too late (also referred to as “retarded”), the engine will run sluggish, get poor fuel economy, and can even overheat.

What To Do if Engine Timing Is Off

If your vehicle has bad engine timing, it’s best to fix it as soon as possible. Consider some of these common repairs:

Adjust the Ignition Timing

If your engine’s ignition timing is off, you’ll have to adjust it to the correct setting. You can do it by yourself if you have a wrench, timing light, and helper, but it’s best to leave it to a professional if you want to play it safe. However, keep in mind that newer engines don’t have timing that can be adjusted by the mechanic.

You can expect to pay around $50 to $70 for an ignition timing adjustment, but the exact bill can vary depending on your vehicle’s make and model.

Replace Your Timing Belt

In most cases, a faulty engine timing chain or belt is to blame for a delay in your engine’s cam timing. A timing belt replacement can cost you anywhere from $10 to $200, but the price can still vary depending on your vehicle’s make, model, and the product’s brand.

Rebuild Your Engine

Does your vehicle have an interference engine? Because if it does, then the stakes might be a little higher when it comes to bad cam timing.

An interference engine is a type of engine with a smaller combustion chamber and larger valves. A small slipup in your engine’s cam timing can cause your valves and pistons to collide or interfere with one another. This impact can damage your valves and pistons, leading to an expensive repair bill.