03 grand am. loud knocking from upper intake. code P0306

Never had trouble before just hit 100k. I was at a stop light and a sudden knock came out real loud. I parked it and had it scanned and I got a code p0306. I replaced the wire, plug, and injector for cylinder 6 only and it's still there. The coil is good as well so now I'm stuck. It sounds like a valve is broken or something. When I pull the wire off the plug the knock goes away and it just misses. Also the knock is very rythmic but misses every so often. Any Ideas or suggestions? posting.php?mode=post&f=1&sid=a3c65992bd7a8813295efd04abfb14b7#

Sounds terminal! When you remove the wire you take away the spark which takes away the load from that cylinder and that's why the noise gets better or goes away. The only thing you can do is remove that valve cover and make sure the rocker arm(s) are not broke and if they are ok then you have problems with the lower end.

i have seen many of those that the bolt holding the rocker arm strips out. if thats the case its an easy fix get a 12x1.25 helicoil kit and your good to go. if not sorry about the motor. at least #6 is on the front side and easy to get to

wow! that's exactly what is was. a stripped rocker bolt. you guys are fuckin awesome! thanks!

You said that you have seen many. What are the conditions of these motors when you saw the stripped threads. I have not seen one yet or heard about it.

Is good to have some tell tale signs beside the noise