The self-tuning PID/I controller (ST-PID-2) with new algorithm of tuning of test signal is proposed. This controller is based on the self-tuning PID/I controller (ST-PID-1) but have better algorithm of tuning of test signal. It is assumed that plant is described by first order with time delay. Coefficients of plant are unknown and can be changed in some isolated time moments. Self-tuning PID/I controller for the plant is proposed in the presence of unknown-but-bounded external disturbances. The test signal with sum of two harmonics is used for identification of plant coecients.To guarantee the stability of the closed-loop system the special switching technique between I- and PID-controllers is used. The I-controller is selected to provide stability of the plant independently on its mode. The obtained results are supported by experimental applications.