Main engine #3 unit exhaust temperature going high - Deviation alarm. We changed the injectors and tried out

Main engine #3 unit exhaust temperature going high - Deviation alarm.

We changed the injectors and tried out one day later again deviation alarm. We changed the exhaust valve and similarly one day later again same alarm. Then we changed the suction valve and ELFI valve. Same result.

Engine parameters were ok for one day but slowly exhaust temperature climbing to deviation levels eventually.

It seems previous crew changed the offset too much to bring no 4 Pi down but the actual value was less (the fault was with the indicator cock).

Reduced rpm from 89 to 79 but still the deviation values are far apart.

We also sent all details to MAN technician and also to Maker.

What could it be due to?

Measures taken: #3 unit Fuel injectors, exhaust valve, ELFI valve, booster pump suction valve changed. Indicator cock also overhauled

Present Status: All units exhaust temperature below 350°C only unit 3 going 400°C.

Update: We changed CCU3's MPC board and got a mild improvement in some units