The engine code C1878 is the main thing to check is to verify the operation of the VCT solenoid. You’re looking for a sticking or stuck VCt solenoid valve triggered by contamination. Refer to vehicle specific reparation manual to perform module tests for the VCT unit. The diffusion method of cylinders is achieved by liberating a synchronizer pin that typically interlocks the cam follower and rocker arms. The engine C1878 code determinations the synchronizer pin is released using hydraulic compression which is controlled by an enthusiastic solenoid. Do not use the car until the car engine is solved. A test drive is necessary.