Cylinder 5 Misfire

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gillygong

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To @powershift ‘s point, are you aware of whether or not the engine has been overheated substantially?

For the Seafoam experiment, yes, just the regular Seafoam spray ought to work. Spray into the cylinder, leave it for a bit, spray again…I’d do 3-4 treatments of it if you have time, letting it soak for 15 minutes between. It probably won’t be a magic fix, but it’s not invasive and it won’t hurt.

On your video, I thought I saw some kind of deep vertical scores on the cylinder wall? I’ve seen one ring break and the broken end cause scoring like that (in a Ford), but I think that’s very rare.
I have a service record that describes an incident where the original owner pulled into the LR parking lot saying the low coolant light was on, and that when they opened the hood the reservoir was empty. Front crossover had sprung a leak, and was replaced. I have no idea how long it was driven with low coolant on the way there. That was at 90,000 miles and I'm at close to 150k now.

For the seafoam, would I need to siphon any back out afterwards? Or just let it burn off by starting the motor.

I think I see the vertical lines you are talking about, but they didn't seem deep?
 

gillygong

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At 20-30 seconds in on the first vid, it looks like pitting on the cylinder walls along with coolant. There is some suspect surface area there. I would re-visit that pitted area to get better video keeping it still on that one area so you can inspect the cylinder wall. If its pitted then the rings wont seal over that surface. It needs to be smooth like everywhere else. A pressurized crankcase can be from blow-by on #5 from pitted cylinder walls. I would think there would be oil burning too. Is there any evidence of circular oil spots on the paint or plastic parts in the rear near the exhaust exits?
There was a bunch of grime at the top of the cylinder which may look like pitting in my terrible video. I'll go in for another look.

I doubt that's coolant, I believe it's leftover oil from the wet compression test- I'm positive I squirted too much in there, and I got a lot of smoke out the exhaust when I started the motor afterwards as the oil burned off. Smelled like burning, not sweet coolant smell.

Oil level has been rock solid for the past 6 months, and no smoke or anything. I'll search around for evidence like you suggest.

So, what does the job of replacing a piston ring look like? Can that be done at home or without pulling the engine? How immediate of a concern should this be? It keeps coming back, but is also intermittent (drove for two weeks with no misfire last week)
 

greiswig

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I have a service record that describes an incident where the original owner pulled into the LR parking lot saying the low coolant light was on, and that when they opened the hood the reservoir was empty. Front crossover had sprung a leak, and was replaced. I have no idea how long it was driven with low coolant on the way there. That was at 90,000 miles and I'm at close to 150k now.

For the seafoam, would I need to siphon any back out afterwards? Or just let it burn off by starting the motor.

I think I see the vertical lines you are talking about, but they didn't seem deep?
It's impossible to tell (for me, anyway) how deep those vertical lines are. But the fact that they're there at all is odd to me, given that I can see hatchmarks from the machining still. So something caused that scoring via piston movement.

Seafoam is very thin, and should basically drain into the crankcase except for what ends up on top of the piston. It'll burn off. Just don't put in so much that it hydrolocks or something. ;-)
 

powershift

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There was a bunch of grime at the top of the cylinder which may look like pitting in my terrible video. I'll go in for another look.

I doubt that's coolant, I believe it's leftover oil from the wet compression test- I'm positive I squirted too much in there, and I got a lot of smoke out the exhaust when I started the motor afterwards as the oil burned off. Smelled like burning, not sweet coolant smell.

Oil level has been rock solid for the past 6 months, and no smoke or anything. I'll search around for evidence like you suggest.

So, what does the job of replacing a piston ring look like? Can that be done at home or without pulling the engine? How immediate of a concern should this be? It keeps coming back, but is also intermittent (drove for two weeks with no misfire last week)
Replacing the rings is major work and they would pull the engine out then take apart the very core of the engine, but I don't know that your issue is from a leak around the rings. Just theorizing. It's something to prove wrong or right.
 

gillygong

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Replacing the rings is major work and they would pull the engine out then take apart the very core of the engine, but I don't know that your issue is from a leak around the rings. Just theorizing. It's something to prove wrong or right.
Gotcha yeah I’m hoping it doesn’t come to that. At this point though, with the tests I’ve done, what else could it be?
 

gillygong

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Did you resolve?
I sprayed a bunch of seafoam spray into the cylinder and let it sit overnight. By morning it had drained out completely. Fired it up and it was still misfiring. Cleared codes, and while waiting a week for some ATS 505 oil system cleaner to arrive, been driving it in the meantime and no misfires for the whole week drove a few hundred miles.
 

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