Spark Knock / Pre-Ignition 1995 F150 302
 

Now I know there are many threads about this topic, I just can't seem to narrow down my issue. I have a 1995 F150 with the 302 and its been pinging for a good year or so now. A while ago it threw a check engine light but that turned out to be an o2 sensor which did help out with the pinging. The truck has 110k miles on it and only really pings upon initial acceleration. Every now and then it'll do it under load but that's every once in a while. The truck has a new distributor, motorcraft copper plugs (at 90k), new plug wires and MSD Ignition Coil. We smoke checked the vacuum lines and fixed the only leak we found. The timing used to be set to 10 BTDC but the pinging was so bad that we had to retard it to about 8. With it set to 8 I would think that the truck wouldn't ping but after driving around for a while (say interstate driving for a good distance) the truck pings under initial acceleration and then is fine throughout acceleration. Any help would be appreciated as to locating this issue. The truck doesn't have any codes but does feel rough at idle with the needle floating a little bit but nothing drastic (not sure if this is relevant info but just throwing it in there). Thanks again, just wanting the old girl to run right again.