Is the barrel temperature of the injection molding machine high?

The temperature of the barrel of the PVC injection molding machine is too high, the color of the finished product is not correct, the screw is new, the temperature of the nozzle and the temperature controller close to the barrel is still normal, that is, the temperature in the second and third stages seems to be uncontrolled , I set 160 degrees, and when the temperature is reached, it trips too, but the temperature keeps rising, reaching about 200 degrees. I saw on the Internet that the back pressure was too high and the back pressure was reduced, but there was no response. Regarding the temperature probe, there should be no problem, because after exchanging the first stage and the second stage, the display temperature is also very high, and the screw rotation speed adjustment is also considered to be a relatively low level. But the temperature just won't go down, ask the experts for advice, very grateful!