I have a 2005, 3.8L grand caravan with 75K mi which has again developed a misfire. There are no electronic codes or indication with scope. The misfire is erratic but frequent when at 50 mph and slightly accelerating. At idle and under strong acceleration there is no miss. No carbon

This happened once before. The dealer finally pulled the head and found one valve with pitting. Regrinding and reassembling solved the problem for about 20K, just long enough that the extended warranty has run out. This feels like swapping parts without addressing the mechanism that lead to that valve pitting.

So assuming I have a similar issue with a valve or two, what is the root cause that should also be corrected? I do not want to go through this again. (e.g. What should I ask the mechanic to do to avoid it re occurring?) Any idea whether the problem a malformed cam not properly timing a valve, weak springs, valve material of construction has too low a temperature range or strength, etc?)

If there is an upgrade for the problem, what brand or how to specify would be greatly appreciated.