I have a 2005 Ford Freestar still under warranty. The valves have been pinging since about 15,000 miles. This is not "valves knocking" - the sound you can hear when the enging is idling, this is the pinging sound the valves make when you put bad gas in, for example or run too low an octane. I've been running 89 octane in it and the engine still makes the pinging noise, not only on inclines but on flat roads, too.

The dealer wants to replace the Mass Air Flow Sensor. Does anyone know if this will fix the problem? Any comments would be appreciated.

 

The dealer may have run across this before & recognizes the problem.If it's still under warranty that is.If that dont take care of it then they have to repair it again. Since you have warranty still let them do what they want to do.