A faulty engine will display symptoms of its decline. Once several of these symptoms show themselves, you can assume your engine is on its last legs. These are the most common signs that your engine needs repair:
You hear knocking noises coming from the engine.
The engine behaves inconsistently when in use.
You can smell exhaust when you drive.
You’re burning through fuel faster.
There are oil puddles under your vehicle.
There is black, gray or even blue smoke coming out of the exhaust.