This is 2006/2007 Hyundai Accent. Normally for u to diagonise correctly u will definitely need some information from the owner or whoever is managing the car because there maybe some intermittent issue that might not happen even if the car spend a month with u because u might not be able to drive it to cover some certain trips. So for you to do that correct u need to gather information from the owner, the one u get in the course of scanning and the physical ones that see when u look around. When I saw the car, it was seriously jerking and I asked about what as been done on it and he said he has changed the coils . I told him the major problem here is still the coil but if one is not very sure... u will be confused from the customer information. He said I just changed it and I said it is not fine. He eventually agreed we should change it. So the jerking reduced like seriously. And also when I scanned and I discovered it is misfiring I tried to check through life data which I discovered the fuel trim is ok and most of the misfire when the fuel trim is ok is caused by blown gasket. I open the engine cover and see little milky substance that may be as a result of mixed oil and water. But for me to be ascertained I had to followed it up with compression test when I discovered there is two adjacent cylinders that have low PSI. That mean where the gasket is perforated is between the two adjacent cylinders that have the low PSI though will don't conclude like that because we still have to check for pistons ring with both dry and wet tests and also make sure the valve seal too is firmly ok. The compression might not be as a result of blown gasket alone but pistons ring and valve too but they all ok except gasket.At the end of it all both the owner and I are both happy.