Have you changed the coolant, or added some recently? Air in the system?

 

I pulled the spark plugs and replaced them and it was still running like crap so I went to take the wires back off and one fell apart, after I changed them it is now running perfect, but still pulling the ect sensor code, I just took it in the have the timing belt and water pump replaced and they are going to do an oil change and coolant flush and replace the oil pan gasket and some other stuff, Im still not really sure whats up with the ect sensor code or if I should even worry about it since the car is running normal.