Symptoms of an incorrectly installed timing belt or chain

There is no doubt that almost all drivers know that the timing, either belt or chain, is an extremely important car part for the engine, and it needs to be changed at some mileage number or a certain amount of time.

Although this change is not made often, it needs to be done for the engine to run properly for a long time. And, for this operation to be done correctly, you need to go to a respected and authorized car workshop, so as to not have unpleasant surprises later.

If you’re interested in the differences between timing belts and timing chains you can read the article I wrote about them.

But what if the timing belt or timing chain was installed wrong?

Sometimes we make mistakes in choosing the right workshop for this kind of operation that requires some skills. On the other hand, there are also unforced errors of mechanics that forget to do just one simple step, leading to incorrect timings in the engine, and to possible damage.

Today we will talk about possible signs of an incorrectly installed timing belt or timing chain.

1. Specific engine noise

You will notice that the engine operating sound is not as usual and changed, or another noise might appear. This happens because the valves do not close at the proper timing.

This is usually the first symptom that appears and that can tell you that you have a timing belt or chain wrongly incorrectly installed.

2. Engine power loss

Here I will go into further details on power loss in correlation with the valves. The camshaft synchronizes the opening of the valves at the right time, in order to have the ideal engine compression, the ideal efficiency, and to obtain the engine power promised by the car manufacturer.

If the camshaft does not transmit to the valves the opportune moment for their opening, to be more explicit, if the timing belt or timing chain is mounted one tooth left or one tooth right, then the valves will not open at the right time. This may or may not lead to disastrous effects on the car’s engine.

Most of the time it’s not something so bad as to completely damage the engine, but it’s enough to keep the intake valves open longer while the piston goes up and then the air in the cylinder comes out when it shouldn’t.

Whether the engine is petrol or diesel, the air entering the cylinder is compressed, but because the timing belt or chain is not installed correctly, the air in the cylinders comes out, and that means air volume is insufficient, the injector will spray the amount of fuel it normally knows that will lead to an improper air-fuel mixture, too much fuel and not enough air, and that will lead to engine power loss, and increased emissions.

3. High fuel consumption

The number three symptom that an incorrectly installed timing belt or timing chain has is high fuel consumption. This results because of the bad air-fuel mixture that I talked about above.

4. The engine might not start

Another cause of a timing belt or chain that is installed wrong.

In the timing belt vs timing chain article I talked about interference engines and non-interference engines.

Interference engines are newer models and if the timing belt or chain brakes, then the pistons will hit the valves, causing important damage like bent valves and pistons.

Non-interference engines are older models, especially petrol cars, which have a lower compression ratio. This means, that when the timing belt or chain breaks, valves are not hit by pistons, and the engine will not suffer any damage, it will just cause it to stall and after changing the timing kit, it will work as before.

5. Check engine light is on

If the Electronic Control Unit (ECU) senses that the engine is not functioning properly, the “Check Engine Light” or MIL will appear on the dashboard.

Often this will be triggered by the camshaft position sensor or crankshaft position sensor because these two sensors record signals that are not correct, leading the Check Engine Light to appear as error P0340 (camshaft position sensor) or P0335 (crankshaft position sensor).

How to know that the timing belt or chain is installed correctly?

As I said at the beginning of the article, installing the timing belt or chain wrong could be due to unforced errors of the mechanics.

This can happen a lot in car workshops. It often happens that mechanics put one tooth wrong, that small mistake does not damage your engine, but it will certainly cause the engine to not run properly.

There is a way to know if the timing belt or chain is installed correctly. When you go to a workshop to do this operation, tell the mechanic (and insist) to do the test below after the change was made.

The final test is to rotate the engine by hand. To do this, grab a large key, put it to the crankshaft pulley, and rotate the engine. When a complete rotation is done, and you did not feel any jamming, and the movement is clean, that means that the piston did not hit the valves, and the timing belt or chain is correctly installed.

This method is good for a mechanic to know that after installing the timing belt or chain it’s not a risk to turn on the engine 🙂


Installing the timing belt or chain the right way is important for your engine. Errors can be made even by experienced mechanics, but knowing these small tips can save the mechanic (and you) from other problems that can be encountered when changing the timing kit.

Often, car manufacturers require that after changing the timing belt or chain to do an emission test, however, I don’t think this is necessary if the changing operation goes well.

My advice is to go from the beginning to a trusted authorized service center. Even if labor is more expensive, there is a lower chance that the change will not be done properly.

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