X2 , pull the valve cover visually inspect for chain slack.

 

Well I drove the car all week, never a light. Saturday night took it on prolly a 100 mile round trip. Ran flawlessly. Stopped on the way home and on restart bam light within a min. Cleared it go to move car today bam light immediately

decided to spend a couple hours today on some diagnosis. Pulled valve cover, chain looks damn near perfect almost no slack. So while cover was off I decided to do a leak down test on 4. I’m getting 40%. Could hear air couldn’t find it, pulled O2 sensor bam I can feel it. So guess it all points to exhaust valve now. On my leakdown gauge 40% is right on the good to moderate leakage line, so maybe that’s why it’s been so intermittent.

 

So, you clear codes without reading them? Are you assuming they are all the same?

 

Almost no slack? That means it's stretched.

40% leakage is really bad.

Correct, seems like a bad exhaust valve.

Or the piston pushed down a little, opening the exhaust valves.

There's some interesting information in this thread. I had a new Harbor freight tester, it needed modification. https://www.chevyhhr.net/forums/how-...-engine-56053/

 

its 304. It’s always 304

 

P0304 indicates a possible burnt exhaust valve

https://www.obd-codes.com/p0304

And other components to investigate

 

Yeah, 40 percent will get codes.

 

Blue- from the list in the link:
spark plug is new
coil pack/wire is new
front O2 sensor is new
fuel injector is new
lots of fuel in the tank

I do occasionally have an odd exhaust smell, which did make me think converter. however i would think if there was an issue with the converter i would be getting multiple cylinder misfires not always the same cylinder.

compressions is low at 125, leak down test shows its going out exhaust.

RJ- i've seen photos of bad timing chains where they have sag in them, not the case with mine. not sure what word to use to describe it other than it looks good. also given i have never had a code related to the timing chain make me doubt any issues with it.

I also rotated the engine to ensure I was getting accurate 100% valves closed numbers, the lowest i saw my leakdown gauge go was to about 35% when putting pressure on to close valve. still much more than what is considered normal.

to me, all signs point to the head needing removed. at this point thats more work than I want to do to the car so i'll likely send it on down the road

 

AC Delco 41-103 Iridium plugs?

 

the numbers on my plugs don’t match that but they are iridium.
ac delco
41-103
12625058