1997 4.6 Spark Knock Issue
The vehicle is a 1997 F150 4.6 Auto 4X4. At highway speeds, it wants to spark knock pretty consistently when the engine is under a load. Third gear climbing hills is the worst, and even overdrive cruising up moderate hills is bad too. It seems to only want to do it over 2300 RPMS. I am getting good fuel mileage, well, normal fuel mileage. I haven't seemed to have lost any power. When I use premium fuel it seems to help quite a bit. I have heard that 3 probable causes are knock sensor, mass air flow sensor, or carboned up engine. I have tested the Mass Airflow Sensor with a multimeter and it tested perfect. I have been running injector cleaner such as Seafoam and Techron quite a bit lately, so I don't think its a dirty engine. I have been told that the knock sensor is located in the middle of the valley, under the intake manifold. What else could it be? I want to rule out all I can before I take the top of the engine apart. I have no check engine light and no trouble codes.