Pontiac Repair: P0300 Random Misfire 2003 3.1L Grand Prix SE, p0300, valve train

Question
My wife's pontiac has a p0300 misfire code. Swapped coil packs, spark plugs and even fuel injectors.  The code is still there.  During my diagnose i also heard a tapping noise comeing from the engine.  With my scanner the misfire happens in cyl. #3 the most. What do I have to look for next. I am in a bind.

Answer
Hi Rudy:

well a p0300 is a random misfire meaning the engine is misfiring but not bad enough to the engine computer to know exactly for sure which cylinder is misfiring but if on a scan tool it shows up as #3 I would ertainly look there first. take a compression reading on that cylinder and a few others and see what you have. If you have a tapping noise it's valve train related maybe you have a broken valve spring on that cylinder or a lifter that is bad and it's not opening the valve(s) enough. just a few ideas it look like you covered all the basic things. Good luck :)