I'm new here guys and I need some help. I have a 1986 F150, 4.9 six with a one barrel carb. The truck has 108,000 miles and is good shape with one glaring problem....it pings under partial throttle all the time. It's driving me nuts. I've tried higher octane, but the pinging doesn't stop. It has been doing this awhile....maybe moreso after I overheated it last winter when it was frozen and I drove it a few miles before I noticed (not enough anti-freeze and no dash lights.....what can I say ?) My mechanic replaced the water pump and it has been fine, but the pinging is making me batty . The truck does ok under a load, but at partial throttle....PING, give it gas, no ping, let off the gas, no ping.....partial throttle, almost any gear P I N G ! My mechanic says smog stuff may be the problem (I'm not buying that) and says my timing is alright. Help me out....PLEASE!

 

Try disconnecting and plugging the vacuum hose that goes to the EGR valve, and see if that makes a difference.