When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Why would you need a hoist? The engine drops out the bottom.
P0300 DOES NOT mean "random misfire" It means "misfire detected". That can mean that the chain is loose or many other things. The way the ecomputer detects misfires is by comparing the actual crankshaft position to the predicted position.
Hi everybody I'm new here. I just picked up a 2010 HHR 2.2.L from a friend of mind, It has been sitting for a couple years after his mother passed away, anyways... he let me have it and flat bedded it over to my house. First thing I did was perform an oil change. The filter was collapsed and gummed up with sludge, damn thing looked like really crappy chocolate cake. I said screw it and replaced the filter and performed and oil change, To my surprise the thing ran alright besides a random misfire. I had codes for the cam solenoids too so I replaced those, it ran a little better. I ran some liquid Moly in the engine and did another oil change and the miss got a little better. Did it again with Seafoam and it ran slightly better still. I drove the car down the road a few miles and back without the check engine light even coming on but the misfire was still there. I knew what I had to do... take apart the engine and clean all the sludge out of it. The sludge is milky and not baked on, I think I lucked out. The car doesn't overheat, I did get a flash of the oil light but no nig deal. It runs pretty damn good for being neglected so I can't see myself swapping the engine out. So far, I removed the valve cover, the intake and the oil pan. Next, I'll be getting that timing cover off, the exhaust manifold and the cylinder head. I'm hoping I can just clean the crap out of all the parts and replaced the timing cover/oil pump and timing components associated with it. Just wanted to share my experience. Do your oil changes and run intake and fuel system cleaner.
if you ever have a next time….might try 4 quarts 10w-40 plain oil ( cause only in there temp.) and 1 quart automatic transmission fluid….and crank it let it run till fan cycles and shut it off, repeat many times. Transmission fluid has a lot of detergents in it. It will clean em out pretty dang good. Had same issue on my 2011 bought used. I dont think those people ever put synthetic oil in it.
I dont have a lift in my garage so dropping the subframe and raising the body is not really an option for me. I just want to lift the block and head out from the hood so I can take it all apart and clean it up and reassemble it. There is plenty of room seeing as i just have the block and head to remove from the engine bay. I know the misfire was related to the timing but I wasn’t about to do anything to this engine without fixing my sludge problem. There’s no way enough engine oil flushes and additives would have cleaned up this mess. Parts washers and brake clean work miracles. Ill be posting more pictures as I dig deeper.
Last edited by GrumpyMrGrouper; Aug 15, 2025 at 01:38 PM.
Such is life on both sides of the planet, mothers do not burden themselves with excessive care of engines. And given freedom, they will buy oil in grocery supermarkets. My late mother, may she rest in peace, brought her engine to about the same state. I have been cleaning this nasty thing for a whole year and still suspect that the carbon and deposits on the piston oil scraper rings have not been eliminated. At least the oil-guzzler has not disappeared.
Hell yeah! I got the head off and I've tore it all down and I'm glad I did, found #1 exhaust valve with a flat face and crack on one side. This explains the P0300 Random miss. On my scan tool it showed the miss was from #1 cylinder, the scan tool was right. The rollers on the rocker arms are choppy as hell probably from the crap in the bearings. I cleaned out the lifters, there was so much crud in them. Looks like now I'll be replacing an exhaust valve, all the lifters and rocker arms while I'm at it. Exhaust Valve crack and flat spot Flat and crack on the #1 exhaust valve
