DTC 0308 and 0300

On my 06 1500 Z 71 LT I got a misfire on #8 Cylinder, looked it up, the info says most likely cause is bad coil. Replaced coil, now I got 0300, misfires all over. The Internet says could be compression, well I got good compression, new spark plugs, new wires, (NGK 51033 Wire Set) NGK doesn't make crappy stuff. I replaced the fuel pump a couple of years ago so I imagine it's ok... So that leaves me with fuel pressure or position sensors, are these testable in the drive way or is it just more effective to replace them? I have no idea where they are but I bet they are in a tough place to get at....
Any insight, tips, or sympathy would be appreciated!

I have heard where leaking intake gaskets can cause misfires.

How old is yours?

Well, in my post I mentioned it was an '06, it has 174k miles. I don't thing I got a leaky head gasket but I'll check anyway, is ether still a good thing to use to check for intake gasket leaks?

dna9656 said:

Well, in my post I mentioned it was an '06, it has 174k miles. I don't thing I got a leaky head gasket but I'll check anyway, is ether still a good thing to use to check for intake gasket leaks?

Click to expand...

I had my intake gaskets, not head gaskets, replaced with Felpro gaskets several years ago.

My truck is a 2004.

If those on your 2006 are original, then they are probably due.

This has been reported to be a fairly common issue.

Well i guess I'll pick up some spray either or put some gas in a spray bottle and do the old leaking intake gasket test... intake gaskets "due for change?" who ever heard of that? Is GM using gaskets made of organic material nowadays?

I wish you the very best of luck with your repairs.

Thank you!