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?
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.