My 1992 F-150, 302 V8, spark knocks when under a load--not while sitting still. Usually does this when starting from a standstill, when accelerating through a turn at low rpms, and accelerating up a grade in 4th or 5th. I fed both tanks with "Seafoam" which helped a bit, but the knocking is still there. Could this be something a problem that a diagnostic test could locate? Any suggestions?

 

How long has this been going on? You might want to have your timing looked at. I believe to get rid of detonation your timing needs advanced. But there could be something else going on to cause it. Wouldn't hurt to try advancing your timing a little to see if it clears up.

 

before you play with timing try running a higher grade of fuel. if that dosent work or just costs to much than retard your timing a degree or two.

 

I had a similar problem in my 91 F150 with 351W. I replaced the O2 sensor and the problem went away. I don't know how you check the sensor, I just suspected that it was probably getting old so I replaced it.

John.

 

I had the same problem in my 89 F-150 4x4 i tried a higher grade of gas and it helped some but later it got worse and come to find out it was the timing . I would try retarding it a couple of degrees.