Such signs as the rough engine operation and decreased thrust indicate that the fuel injectors may be clogged. To prevent clogging, it is required to flush the nozzles. There are two main ways to do it. First, it is possible to flush the injector through the fuel rail, in which flushing fluid is supplied to the combustion chamber through the rail, with which the engine has been running for some time, and the process also includes replacing the spark plugs. Ultrasonic cleaning of nozzles is carried out if more serious flushing is required: for this, the nozzle is removed and placed in an ultrasonic bath.