I have changed spark plugs,was running great then it started to over heat nowski

Hello, what was the original cause of replacing your spark plugs? Overheating sounds like a more serious concern, check your cooling system first for functionality, your thermostat operation, water pump for proper operation, possibly you could even have an internal engine coolant leak if you are getting misfires. I recommend a qualified technician have a look at your vehicle for a diagnosis.