Help with 05' neon 2.0 sohc

OK so the last 3 days, I noticed my 05' neon 2.0 sohc N/A daily driver was pinging, under very light throttle at first, could barely even hear it. Figured, no big deal, probably bad batch of gas or something. Well, yesterday it got much worse, much louder pinging and under most forms of acceleration. Well today, the crap hit the fan I guess. I drove to lowes, same symptoms as yesterday, but when I started it up at lowes to leave, it was seemingly only running on 3 cylinders at idle, fairly rough idle, and pinged BADLY on any acceleration. Limped it home, checked the codes. P0304, which is cylinder 4 misfire. So I pulled the spark plugs, they all looked fine mixture wise (black rim around the base of threads, porcelain just slightly discolored but mostly white) except cylinder 4 had molten speckles of aluminum on it. So, I did a compression check. From 4 to 1, 85/105/145/155. Now this was engine cold, holding WOT, but thats still pretty bad on 3-4. Friend of mine suggested I try a trick, pour about a tablespoon of oil down the spark plug hole and see if compression rises and this will tell if the problem is bottom end or top end. So I did that on #4, it bumped compression to 145. So it sounds like perhaps I just have very worn rings. But my question is, I've never seen this cause pinging, especially with a 3 day progressively worse extremely rapid decline. 4 days ago, engine was running like a top zero issues, but I never did a compression check so hard to say what it was then. Just wondering if anyone else has had experience with a similar issue and knows exactly what the problem is. I just find it hard to believe that this is a simple worn rings situation, but perhaps I'm wrong. Now one more thing, if I free rev to about 2k rpm, it makes a funny sound. The best way I can describe it is if you know anything about computer fans its the sound that a fan makes when the bearings are going out and the fan is in imminent death.

Any advice/experience/etc would be appreciated. I don't know much about the 2.0 sohc engine other than it got me 30-34mpg as a daily driver lol.

I would suspect the detonation must be due to either running lean, or oil infiltration into the cylinder lowering octane enough to cause knock. Either way, it sounds like you're in need of at least one new piston on that engine.

Sounds like it could have been a failing, clogged, or partially-clogged #4 injector leaning out that cylinder. Either that or you've got overall fuel problems and #4 fell victim as the weakest link.

With the symptoms and your description of the spark plug, it's almost certainly too late. A bore scope would give you your last bit of confirmation short of ripping it all apart.

I'm wondering if you could find a 03-05 engine for less money/aggravation than tearing into what you have.

I pulled the rail and cranked the engine over, injectors firing perfectly!

Need to check cam timing.

If the cam timing was off, it most likely would have thrown a cam timing code.

Cam timing was right on.

Ended up just pulling the head then, and found this! Mystery solved. Kind of odd to blow between cylinders.

Kind of odd to blow at all. Those MLS headgaskets can survive a lot of abuse! Good to see that it was something simple (simpler than pulling a piston at least).

Yeah I had the head checked for cracks in case that was the cause, but the head was fine so it's kind of a mystery. Perhaps a bad head bolt or something, it got fatigued over time enough to let the gasket pop. Thats my best guess anyway.