I dont really have any good idea why it would be pinging. What I think of as ping is also known as 'detonation'. It isnt usually much of a problem with Escorts/Tracers, from what I can see on the forum. It can be due to an engine running lean (as the result of a fairly large vacuum leak) or the engine overadvancing (also seldom a problem with an Escort/Tracer). Assuming it is detonation, I suppose it could be a combination of things. For example, an EGR system that is letting in outside air instead of only exhaust gases (a cracked EGR tube for instance), or the fuel pressure regulator not keeping the pressure in the fuel rail up when it should. (It should be higher when the throttle is open, and should be lower when the throttle is shut). The regulators dont fail enough for me to know what their manner of failure is. I dont know what the symptoms would be if the mass air flow sensor in the air filter housing was obstructed, but you might want to have a look at it.
If its detonation, it should do it less when you put in a tank of high octane gasoline. This wont hurt the engine.
If the noise is actuaally valve related, I can only think that maybe someone had re-installed the lifters backwards, and they arent getting the oil supply that they should. Hopefully it isnt a valve seat coming loose in the engine head. That certainly happens often enough to be a known problem in Escorts/Tracers.
