what car? If you have the cheap OBD2 scanner (BT/wifi) that can read your ECU, then may be easier to know whats going on witht he engine and its subsystem. Thing like LTFT. STFT, lambda sensor reading etc can give you an idea on your next step, not shooting in the dark like now.

I think there are some who is well versed in interpreting these ECU readings here that may be able to help you.