I have a 94 Explorer Limited.
Nasty ping on acceleration when warm.
No ping while engine is cold.
I have looked at the EGR valve, the ports are clean.
Had to replace the vacuum lines to the EGR transducer.
The diaphragm is good, it will compress and hold with vacuum applied. Hooked up a vacuum meter in line with the valve and took it for a ride. Max vacuum readings were 12-15 pounds.
So.. the EGR looks ok, has vacuum and appears to operate properly.
The next test involved putting a timing light on the harmonic and repeatedly tapping the head. Thought I should see the timing retard, it didn't. This leads me to believe that the knock sensor is dead. I have purchased a new one ($60 bucks, thank you very much)but have yet to install it.
Is there anything else I can check?

 

Pull out the MAF sensor and clean it if the probes look dirty. I had a some pinging problems on my '94 Sport. The MAF sensor probes were VERY dirty. Cleaning it helped tremendously.

 

Thanks.
Looked at some of the older posts, (should have done that first)most suggest the mass airflow. I'll give it a try.

 

That was it!
Horsepower is up and no pinging.
Would'a never thunk it.
Thanks again!