I have 89, F150 that when you accelarate, it makes a loud pinging noise. Sounds like when you use bad gasoline. I have changed plugs, wires, distr. cap. checked timing. Had vacum checked. My machinic said it may be EGR valve, he said it was operating, but slowly. Any suggestion before I spend big bucks on egr valve?

 

you could try running higher premium gas that helps it burn smoother but the EGR is probable due to it cools the combustion area and lets the fuel burn more effeicently which is what casues the fuel to ping if it gets too hot in intake area ..combustiona rea the fuel will ping so thats prob the best solution to make a final fix.
Godbless
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