Q: Muffler smoke after doing repairs on the car

Most likely, the work you had done and the smoke are unrelated. Black exhaust smoke indicates a rich air fuel mixture and can be caused by problems like a leaking fuel injector or faulty engine sensor. White exhaust smoke indicates coolant is leaking into the combustion chamber and can be caused by problems such as a leaking head gasket or cracked head. Finally, blue-gray smoke indicates that the engine is burning oil. This can be caused by issues such as worn valve guides or piston rings. I suggest you have a trained professional, such as one from YourMechanic, diagnose the smoke that’s coming from the car firsthand.