Signs of a Bad Exhaust Valve

Updated July 19, 2017

The exhaust valve is a component on your car that transfers burnt gases from the cylinder to the exhaust manifold. If this valve goes bad, there are certain symptoms to be aware of to diagnose the problem. These symptoms include a bad odour, misfiring and no compression on the cylinders.


The first sign of a bad exhaust valve is misfiring at low engine speeds. Misfiring occurs when the engine loses its power, and the driver feels a jerking action as a result. This happens because of a leaky exhaust gasket, which causes the valve to burn at high speeds and temperatures.

No Compression on Cylinder

Check the compression of each of your car's cylinders. If you don't have any compression on a cylinder, this means that you have a burnt-out or bad exhaust valve. If there is no compression on a cylinder, the car is running on less cylinders than it should, which can cause the engine to run slower and become damaged easier. Compression can be checked using a compression gauge or engine analyzer.

Irregular Exhaust

Another symptom of a bad exhaust valve is smelly, black-coloured smoke coming from the exhaust pipe. If this is the case, you may need to replace both of the manifold gaskets to resolve the issue. The smell coming from the exhaust pipe will be similar to that of rotten eggs. The O2 sensor, plugs and wires may need to be replaced as well.

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