Well, my 2003 Durango 4.7l has developed a metallic tap/tick hard to describe really, around the passenger side area more top end sounding and isn't continuous, missfiring badly and have to give it gas to start and check engine light flashes, only code is p0300. Pulled the passenger side valve cover and all the rockers are in its place etc, just cranking it over it doesn't make the noise but the cam sensor has some very fine metal dust on it not sure if its related. Pulled the plugs and they all look good. The engine has 308k on it and my parents have owned it since new with regular oil changes. Tempted to remove the driver side valve cover to see but it sounds as if the cam is hitting a rocker that fell off. It smelled very rich too. Rocker arms, chains and stuff was done at 278k miles. any thoughts? It was great till half way to work yesterday and just became very rough and sluggish. To accelerate from a stop it wouldn't respond to throttle till about 25%+.

 

Might be a valve seat, in which case you won't be able to see it without pulling the head. Sometimes the actual location of a sound can fool you. Might be something on the driver's side though, so go ahead and pull the other cover. You can loosen the brake booster down by the brake pedal to allow for clearance. Keep checking the codes, it might pop one with the actual cylinder, vs multiple cylinder misfire. You might want to take out all the hydraulic valve lash adjusters (aka lifters) and see if they are actuating properly. One might have seized. I'd just replace them since you're already in there.