What Happens If Timing Belt Is Off By One Tooth? [Explained]

If the timing belt is off by one tooth, you may face problems like engine backfire, engine misfire, damaged valves,  poor performance, poor fuel efficiency, etc. Most importantly, the engine might stop working after driving a certain distance. 

This is just an overview. Continue reading for more details.

Symptoms of Timing Belt Is Off by One Tooth

There are symptoms that indicate if a timing belt is off by one tooth. These symptoms of timing belt tooth slippage sometimes differ with the type of engine.

There are two types of engines depending on the contact between the valves and pistons. These include an interference engine and a non-interference engine.

An interference engine has no gap between the pistons and the fuel inlet and gas exhaust valves when the piston has reacted with the topmost part of the engine cylinder called the top dead center (TDC). Conversely, non-interference engines have a gap between the pistons and the valves when piston reach TDC. For this difference in their characteristics, the symptoms also differ.(1

Symptoms of Timing Belt Is Off by One Tooth

The following table compares the symptoms in interference and non-interference engines:

SymptomsInterference EngineNon-Interference Engine
Possibly the engine won’t runYesYes
The piston and valve will bend awayYesNo
The engine may make noises such as knocking or tickingYesYes
Engine will run poorlyYesYes
Misfiring or stallingYesYes
There may be a loss of powerYesYes
Check engine light may appearYesYes
Misaligned or damaged timing beltsYesYes
Belt and pulley timing marks may not line upYesYes,

What Happens If the Timing Belt Is Off by One Tooth in Interference Engine?

Here are the effects of the timing belt being off by one tooth in an interference engine.  

Damaged Valves

When the timing belt is off by one tooth, the engine’s valves will open and close incorrectly. For the incorrect timing, the engine piston and the valve may collide badly in an interference engine. 

The ultimate consequence of this factor is damage to the valve if it remains unaddressed. 


This effect does not apply to the non-interference engine. However, all other consequences of the interference engine are identical to the non-interference engine.

So, check below for further consequences of the interference engine.

What Happens If the Timing Belt Is Off by One Tooth in a Non-interference Engine?

Below are the consequences of a non-interference engine for the timing belt is off by one tooth. Notably, these outcomes are also applicable to the interference engine. 

Engine Backfire/Misfire

Misfires, and backfires can occur when the timing belt skips one tooth. This is because the spark plug ignition must be in sync with the movement of the piston in the cylinder. If the spark plug fires too soon, it can cause knocking and harm the engine. 

In contrast, if the spark plug fires too late, the engine will perform poorly and consume more fuel. The timing of the ignition is crucial to the engine’s smooth operation.

Reduced Fuel Efficiency

An engine may not run as efficiently if the timing belt is misaligned by one tooth, resulting in reduced fuel efficiency.

Timing belt misalignment makes the engine overstressed. As a result, it burns more fuel.

Increased Emissions

A timing belt that is off by one tooth can lead to increased emissions, causing the engine to run lean. This means that there is not enough fuel burning in the engine. When this happens, the engine may emit more carbon monoxide (CO), and hydrocarbons (HC), and they’re harmful to the environment.

Furthermore, a misaligned timing belt can cause the engine to run hotter. This can lead to more harmful nitrogen oxides (NOx) emissions.

Rough Idling

Timing belts that are off by one tooth can cause misalignment and slippage. Misaligned timing belts can cause rough engine idling since they synchronize crankshaft and camshaft rotations. 

Misalignment hinders the smooth operation of the engine. Consequently, rough idling occurs.

Poor Performance

The timing belt is typically made of rubber and driven by the engine’s crankshaft. Timing belts synchronize crankshaft rotation with camshaft rotation, which controls engine valves opening and closing.

This whole process needed proper synchronization. Otherwise, the engine will perform poorly. 

These are the possible consequences of the timing belt being off by one tooth. However, this issue is resolvable.

If you notice your car engine jerks sometimes, it’s might be a result of faulty timing belts. It’s better you store some clear ideas about it so you can use them when needed.

Timing Belt Is Off by One Tooth in Interference Engine Infographic

How to Fix The Timing Belt That’s Off By One Tooth? 

Your timing belt needs to be fixed immediately if it is off by one tooth. If you continue driving without fixing it, the consequences will be dangerous. This may even cause your engine to die completely.

Getting back to the point, follow the steps below to fix this issue. 

Tools needed 

  • A socket wrench
  • A digital tension gauge

Safety precaution: Disconnect the battery to avoid any type of electrical accident. To disconnect the battery, first, remove the negative terminal and then the positive one. Conversely, connect the battery in reverse order. 

Step 1: Remove the timing belt cover

Most timing belt covers are mounted on the front of the engine with bolts. Using a socket wrench, remove the bolts and gently lift the cover off.

Step 2: Locate the timing marks

Timing marks are located on the crankshaft and camshaft pulleys and are used for belt alignment. Ensure both pulleys are aligned correctly by looking for timing marks.

Step 3:Correct the timing 

If the timing belt is off by one tooth, you must adjust it to get it back in proper alignment. You will need to loosen the bolts holding the camshaft and crankshaft pulleys in place, move the pulleys until the timing marks align, and then tighten the bolts again.

Step 4: Check the timing belt tension 

Use a timing belt tension gauge to check the timing belt’s tension. You should maintain the tension within the range specified by the manufacturer. Adjusting the tension may be necessary if it is too high or too low.

Step 5: Procedure to measure tension with a gauge

Follow the instruction below to measure the timing belt tension with a tension gauge.

Source: Bestorque

Determine the span length “P” of the belt. For that, apply a force “F” perpendicular to the span to deflect the belt 1/64 inch per 1 inch of span.

Then place a straight edge across the center of the span and use a tension gauge to measure the force “F” at the calculated deflection. Lastly, use the table in the user manual to determine the correct force to apply.

Step 6: Reinstall the timing belt cover

Once it is properly aligned, you can replace the cover and secure it with the bolts you removed earlier.

Step 7: Test the repair 

Listen for any unusual noises or roughness in the engine’s operation when you start it. You can consider the repair successful if everything is running smoothly. The repair may need to be revisited and further adjustments if you encounter any issues.

Depending on your vehicle, you may have to follow different steps and procedures to repair a timing belt. Ensure you follow the manufacturer’s repair manual instructions for your specific make and model.

Maintenance Guide for Timing Belt

By proper maintenance, you can prevent the timing belt off by one tooth and other identical issues. Here are some key points to consider for timing belt maintenance:

  • Replace timing belts according to the manufacturer’s recommendations. Timing belts should be replaced at the recommended intervals to avoid failure and engine damage.
  • Ensure that the timing belt and surrounding components are kept clean. Timing belts can be prematurely worn out by dirt and debris accumulating around them.
  • When working on the timing belt, use proper tools. Timing belts and other engine components can be damaged if the wrong tools are used or if too much force is applied.
  • A mechanic should be consulted if you are not confident performing timing belt maintenance or repairs on your own.


Is There Any Warning Before The Timing Belt Breaks?

Yes, knocking, slapping, or loud clicking sounds are signs of a broken timing belt. Besides these signs, there are other minor ones, such as misfiring and overheating. Symptoms such as these should prompt you to check your timing belt as soon as possible.

Will There Be A Spark If The Timing Chain Is Off?

Yes, there will be a spark, but that won’t be at the correct time. The spark will likely not occur at the correct time if the timing chain is off, resulting in misfires or engine failures. The timing chain must be installed and adjusted properly for the engine to function properly. 


Hopefully, now you know what happens if the timing belt is off by one tooth. However, the whole scenario depends on which type of engine you have in your vehicle. 

So be sure what type of engine you’re using because the consequences are not the same for both the interference and non-interference engine.

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Aaron Byrne

Hi, Aaron Byrne here. I'm an expert automotive mechanic with 10 years of experience. I work on engine parts especially timing belts for their repair, maintenance, and replacement.

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at Autoglobes.com with a passion for the automotive industry.