Originally Posted by Yamae

Sorry to say but I wonder why you step ahead too much without confirming the root of the problem. Your way of thinking will be wasting the time and money more. Actually you have already wasted 4 months and some money. I worry that you will be throwing parts/money next to next. If you don't have any tools to troubleshoot like observing the waveform, simply ask someone capable or a professional to investigate. There is a possibility that timing belt is skipped, a connector is damaged, harnesses are damaged, the connections are poor or others, Things are not so simple, I must add.