Can a bad exhaust cause black stuff on the spark plugs?

Yes, a bad exhaust can cause black stuff on the spark plugs. This is because a bad exhaust can cause the engine to run rich, which means that there is too much fuel being used in the combustion process. This can lead to the formation of carbon deposits on the spark plugs, which can eventually cause the spark plugs to fail.

Here are some of the signs that your exhaust may be bad:

* Black smoke coming from the exhaust pipe

* A strong smell of fuel from the exhaust pipe

* The engine is running rough or idling poorly

* The engine is losing power

* The spark plugs are black or fouled

If you are experiencing any of these symptoms, it is important to have your exhaust system checked by a qualified mechanic as soon as possible.