Hmm, "every once in a while " has me doubting a head gasket issue. They normally don't seal themselves and run fine! I'm prone to going with an overheating issue.
Remove all external engine tins and blow off cooling fins. Running after the key is "off" IS pre-detonation, typically caused by carbon in the heads...creating "hot spots" and igniting fuel. Run some sea foam for a few tanks of fuel and see if it improves. Regular use of sea foam or other fuel additive won't hurt either!
If you do decide to replace the head gasket, remove the bolts & head ONLY after the engine has cooled down. Remove head, clean gasket surface, place on a FLAT surface and check with a .003" feeler gauge. If this goes under head at any point, the head needs to be resurfaced...either by you with emery cloth or my a machining service. Bob
Remove all external engine tins and blow off cooling fins. Running after the key is "off" IS pre-detonation, typically caused by carbon in the heads...creating "hot spots" and igniting fuel. Run some sea foam for a few tanks of fuel and see if it improves. Regular use of sea foam or other fuel additive won't hurt either!
If you do decide to replace the head gasket, remove the bolts & head ONLY after the engine has cooled down. Remove head, clean gasket surface, place on a FLAT surface and check with a .003" feeler gauge. If this goes under head at any point, the head needs to be resurfaced...either by you with emery cloth or my a machining service. Bob
