My 98 f-150 , 4.2 has been pinging for some time now just going down the road then up a slight incline it pings, it is a standard shift and i just changed plugs it has 75,000 miles and runs good except for the pinging is our gas we buy now that bad.

 

Try cleaning the MAF. If dirty, it can cause the engine to run lean enough to ping.

 

what cleaners would be safe for this.

 

I usually use electrical contact cleaner. It doesn't leave a film when it dries. Just spray the wire filiments. DO NOT wipe them. They are very fragile.