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Rough Start - Misifire - Head Gasket Leak?

I'm going to write a book here so bear with me, I've got to give some background. I've posted on here before about my 2008. I've since bought a 2010 and it's doing fine but the 2008 is acting up so I'll take it from the beginning.

Roughly a year ago (exact timing isn't really relevant) my son started reporting that his Jeep (the 2008) wasn't running right. I blew it off somewhat but it eventually completely crapped out. It had absolutely no power and when trying to drive (under load) had a flashing check engine light. I was getting C121C (Torque Request Denied) and P0300 (Random Misfire). Even though it was random I started by replacing the easy stuff first like plugs and wires. When that didn't work I started replacing components and sensors, including the coil pack, camshaft position, crankshaft position, MAP, and probably another 1-2 that I don't remember. At some point during this multi-week evolution it also popped up a P0430 (I think) which was a 'catalyst efficiency below threshold' so I ended up replacing all 4 O2 sensors. Nothing worked. Oddly, I'd see small improvements here and there but it was just coincidental and it always went back to being just as bad as it was before.

I was researching the forums during all this and there was ONE SINGLE post of a guy who had the same codes (C121C and P0300) who mentioned having a blown head gasket. I went down and spoke with my local service manager who asked "has it been run hot?" to which I replied that it hadn't been "run hot" but did seem to be running EXTREMELY hot. I think you get my point ... everything under the hood seemed to be scalding but the temperature never ran up. I asked why and he said he thought I had a blown head gasket. ???? Why would you think that? I have no symptoms, I'm not losing water, I've got clean oil, I'm not overheating. He said just trust me, get a compression tester and check what you've got.


Long story short, I had bad compression on cylinders 2 and 4. I don't recall exact numbers but 2 was low, 4 was REALLY low. So I decided at 150k miles it was time for a rebuild anyway and set out tearing into it. I'd replaced several gaskets and seals at this point so I hated to do this but nevertheless knew that I needed to. After tearing into it, I had one seized compression ring on #2 and both rings seized on #4. So I cleaned up the pistons, put new rings on, honed the cylinders, and slapped it back together with new bearings. To my HORROR, the problem was still there. WTF? The only thing left, and a valid possibility was a bad ECU .... except that P0430 was still lingering in the back of my mind. So I took the Y pipe out and gutted the top 2 Catalytic converters. The top 2 were easy, the bottom two were past bends in the pipe and weren't accessible. I put it back together again and .... SAME thing. So again, with 150k miles, what would it hurt to go ahead and replace the y pipe and get 4 new cats right? See attachments, 1 of my 4 cats (one of the 2 downstream that remained) had completely failed.

Now it all made sense, the backpressure from the clogged cat was causing the excessive heat at the engine/head because it couldn't breathe. And because it couldn't exhale, it couldn't inhale. Since it couldn't get clean air there was no O2 for combustion, only CO2 so it was getting random misfires (P0300 is defined as more one cylinder) so all three one-sided cylinders were stopped up.

Voila, the Jeep was back to normal. Except it isn't.

So here's where I'm at today. Since the rebuild I've been losing water, but extremely slowly. I've got a very infrequent reoccurrence of P0430 (bank 2 catalyst inefficiency). And I've got a nagging misfire, almost every single time I drive it. The Jeep drives great once warm, but it starts HORRIBLE 99% of the time. And the kicker, 90% of the time the misfire is the same cylinder number 4. Doh!

Here's my first question: How likely is it that the seized rings and continued driving prior to rebuild caused enough warping in the cylinder to a) not be visible to the naked eye and/but b) caused bad compression now even after installing new rings?

Second question: How likely is it that I've got a leaking, new head gasket? And how would I go about definitively diagnosing that? For the record, I have no water coming from my tailpipe, but I do have what I consider normal water vapor mist for a few minutes after a start. Yesterday I bought an inspection camera from HF and there is noticably less carbon buildup on #4 piston than 2 and 6. (I'm actually blown away by how much buildup is on the freshly cleaned 5k mile pistons). I've read before, and it makes sense, that water leaking into a piston will "steam clean" the piston head. It definitely looks like that could be happening. 2 and 6 are covered 80-90% in gunk, but #4 is probably 80% clean (comparably). I was hoping to see signs of water "sitting" in the cylinder on top of the piston. That would have definitively told me that I had water leaking and it would have explained the rough cold starts. But no luck.

Any other thoughts? Very rough starts for 10-20 seconds but runs fantastic afterward. While driving, almost every trip results in a CEL and cylinder 4 misfire. Once every week or two, I get a P0430 for Bank 2 Catalyst Inefficiency.
 

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TL:CR

I'm the Lord of runon sentences & even I can't tackle that wall of
info ,man.

so, have you ever had a tuner on this Jeep?
did someone prior to you have one?
did you replace the crankshaft positioning sensor ?




 

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All you did was half assed everything you did. Why would you go through all of the trouble of pulling the motor and doing a half assed rebuild. The engine must have been running very hot to seize the rings to the piston. With the pistons being black I would devote my time and figuring out the p0300 code.

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Did not see it mentioned but did you have the cylinders checked for roundness? If you were going to the trouble to tear down the motor and spend money rebuilding you should have jumped balls deep and got new pistons, if one was over heated to the point of seizing rings I would say it has been suspect of having a ring land failure. The price for pistons on the 3.8 seem extremely low. and to me seems like cheapo insurance. Did you check flatness on cylinder heads? how about the block deck? All things I would have checked if I went into an engine. I have done a bunch of engine rebuilds over the years some of the as basic freshen uppers, others and pretty extreme builds. I have build high horse power SBC naturally aspirated as well forced induction engines, all projects are approached in basically the same manner new pistons, cam, lifters and bears, NEW oil pump every time and at least main and rod bearing replaced. always measure cylinders for roundness as well as diameter. having heads pressure tested is fairly cheap at most machine shops as a cheap insurance policy so money is not wasted on parts.
 

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Discussion Starter #5
All you did was half assed everything you did. Why would you go through all of the trouble of pulling the motor and doing a half assed rebuild. The engine must have been running very hot to seize the rings to the piston. With the pistons being black I would devote my time and figuring out the p0300 code.

I just love chatting with internet tough guy smart asses. Thanks for the insights, you've been helpful.
 

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Discussion Starter #6
TL:CR

I'm the Lord of runon sentences & even I can't tackle that wall of
info ,man.

so, have you ever had a tuner on this Jeep?
did someone prior to you have one?
did you replace the crankshaft positioning sensor ?
If I hadn't put all the info in there, think about how unhelpful chasing a p0300 would have been.

No, and not that I'm aware of. Bottom line, it ran fine for 2-3 years leading up to the clogged cat. This issue is strictly post- repair. And yes, I think I said in there somewhere that I replaced the crank sensor, cam sensor, and darn near every other sensor when I was trying to chase the original p0300 and c121c codes prior to replacing the y-pipe with new cats.
 

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Discussion Starter #7
Did not see it mentioned but did you have the cylinders checked for roundness? If you were going to the trouble to tear down the motor and spend money rebuilding you should have jumped balls deep and got new pistons, if one was over heated to the point of seizing rings I would say it has been suspect of having a ring land failure. The price for pistons on the 3.8 seem extremely low. and to me seems like cheapo insurance. Did you check flatness on cylinder heads? how about the block deck? All things I would have checked if I went into an engine. I have done a bunch of engine rebuilds over the years some of the as basic freshen uppers, others and pretty extreme builds. I have build high horse power SBC naturally aspirated as well forced induction engines, all projects are approached in basically the same manner new pistons, cam, lifters and bears, NEW oil pump every time and at least main and rod bearing replaced. always measure cylinders for roundness as well as diameter. having heads pressure tested is fairly cheap at most machine shops as a cheap insurance policy so money is not wasted on parts.
I didn't pull the engine to rebuild the pistons. I would have if I'd have seen more signs of damage but that's neither here nor there at this point. First, the rings were seized in the piston grooves, not melted to the pistons. They were full of what appeared to be a charcoal type substance, presumably years of burnt oil? Idk, but bottom line is after cleaning it all, nothing looked bad, warped, overheated, etc. As far as checking the cylinders, again the engine wasn't on a bench somewhere but I can say that there were no visible signs of scoring in the 2 and 4 cylinders that had seized rings. That's kinda one of my questions, how likely is it that the cylinder would have been warn enough to have issues now without the damage having been visible.

And completely agree, if the rings had been melted to the piston and the pistons would have likely been discolored from overheating, I would have gotten new pistons.
 

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All you did was half assed everything you did. Why would you go through all of the trouble of pulling the motor and doing a half assed rebuild. The engine must have been running very hot to seize the rings to the piston. With the pistons being black I would devote my time and figuring out the p0300 code.
I just love chatting with internet tough guy smart asses. Thanks for the insights, you've been helpful.
If you don't like comments posted against the thread you started here, maybe you shouldn't have posted. Just get over your hurt feelings on this one and move on.

I didn't pull the engine to rebuild the pistons. I would have if I'd have seen more signs of damage but that's neither here nor there at this point. First, the rings were seized in the piston grooves, not melted to the pistons. They were full of what appeared to be a charcoal type substance, presumably years of burnt oil? Idk, but bottom line is after cleaning it all, nothing looked bad, warped, overheated, etc. As far as checking the cylinders, again the engine wasn't on a bench somewhere but I can say that there were no visible signs of scoring in the 2 and 4 cylinders that had seized rings. That's kinda one of my questions, how likely is it that the cylinder would have been warn enough to have issues now without the damage having been visible.

And completely agree, if the rings had been melted to the piston and the pistons would have likely been discolored from overheating, I would have gotten new pistons.
You have an engine where the block is cast iron, the pistons are aluminium, and the heads are aluminium. Dissimilar materials that expand and contract at different ratios according to the temperatures reached and you've stated it didn't overheat, but was running "extremely hot". Then you don't perform a proper rebuild hoping that it will just work when you don't really know what is out of tolerance for the engine. You don't know if the cylinders are out of round, you don't know if the pistons are out of round, and you don't know the conditions of the heads with the excessive heat. The only thing we know for sure is a clogged catalytic converter caused all of this fun to begin with and you're still having issues with what you already performed.

Knowing myself if I was in this situation, I would have taken the block, the crank, and the heads to a machine shop to go over thoroughly in the first place. This way if the cylinders needed to be bored, the crank needed to be machined, the heads needed to be decked, or some other issues with them, I could make an informed decision with what to do from there. This is my suggestion of where to start as you really don't know the condition of what you worked on in the first place.

What ever direction you go, good luck... :wink2:
 

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All you did was half assed everything you did. Why would you go through all of the trouble of pulling the motor and doing a half assed rebuild. The engine must have been running very hot to seize the rings to the piston. With the pistons being black I would devote my time and figuring out the p0300 code.

I just love chatting with internet tough guy smart asses. Thanks for the insights, you've been helpful.

Not an internet tough guy, I call it as I see it. Since you have no ideal in what you are doing, you jumped in to your engine and started ripping shit apart instead of asking for help a head of time. Now that you did everything wrong now you want help and are going to be pissed that your feeling are hurt. Good luck with future help.


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If you don't like comments posted against the thread you started here, maybe you shouldn't have posted. Just get over your hurt feelings on this one and move on.



You have an engine where the block is cast iron, the pistons are aluminium, and the heads are aluminium. Dissimilar materials that expand and contract at different ratios according to the temperatures reached and you've stated it didn't overheat, but was running "extremely hot". Then you don't perform a proper rebuild hoping that it will just work when you don't really know what is out of tolerance for the engine. You don't know if the cylinders are out of round, you don't know if the pistons are out of round, and you don't know the conditions of the heads with the excessive heat. The only thing we know for sure is a clogged catalytic converter caused all of this fun to begin with and you're still having issues with what you already performed.

Knowing myself if I was in this situation, I would have taken the block, the crank, and the heads to a machine shop to go over thoroughly in the first place. This way if the cylinders needed to be bored, the crank needed to be machined, the heads needed to be decked, or some other issues with them, I could make an informed decision with what to do from there. This is my suggestion of where to start as you really don't know the condition of what you worked on in the first place.

What ever direction you go, good luck... :wink2:
Good to know what you would have done, but there's more than one way to skin a cat right? I am where I am and I'm asking for advice from people who may have experience. There was no catastrophic failure and no reason pull and rebuild the block/crank (heads are new and rebuilt) and we can debate the details as to whether or not this is the same issue as before. It is not. I've got the technical background and education to do this repair and more than hold my own in a debate with folks on a blog. That being said, I'm smart enough to realize that I don't know everything and look for advice when I think I need it. That doesn't mean I want or expect every know-it-all smart ass who can't handle reality and lives vicariously through blog posts to get on here and be condescending. Hurt feelings you say? Not hurt feelings, now I'm just calling it like 'I' see it. You guys clearly have no helpful advice so after these posts today, saying my peace, I'm done on here. I can figure this out on my own reading other posts.

Last but not least and for anyone else who may stumble upon this in the future (because I believe the purpose of these posts is to be helpful), I did figure out that the rough start was caused by an unseated PCV valve. Long story short, when I removed/replaced the earlier one I cracked the pcv seat of the plastic valve cover. Since the new one already had a new PCV valve installed, I didn't bother to make sure it was fully seated. It was not and had worked it's way fully unseated. So that problem's solved.

Bon Voyage!
 

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Not an internet tough guy, I call it as I see it. Since you have no ideal in what you are doing, you jumped in to your engine and started ripping shit apart instead of asking for help a head of time. Now that you did everything wrong now you want help and are going to be pissed that your feeling are hurt. Good luck with future help.


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LOL, you have no idea what my background is and what experience or knowledge I have. Thank you for making assumptions and making an ass out of yourself. There are two types of people on these blogs; those who live on here, and those who come here with questions. I fall into the latter and don't have a problem saying it. You really should learn grammar before you start being a condescending smart ass so that when people read these posts in the future they think you at least graduated high school before offering your brilliant advice. And last but not least, I have asked questions before, ahead of time, and I get the same type of replies from smart asses like yourself who have nothing meaningful to contribute but just want to stroke your own ego and belittle people. I'm happy where I am in life and don't need to put people down for asking questions, how about you? The mechanics that I've been around usually like to teach people the trade, not belittle people for asking questions. Have a nice life.
 

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Good to know what you would have done, but there's more than one way to skin a cat right? I am where I am and I'm asking for advice from people who may have experience. There was no catastrophic failure and no reason pull and rebuild the block/crank (heads are new and rebuilt) and we can debate the details as to whether or not this is the same issue as before. It is not. I've got the technical background and education to do this repair and more than hold my own in a debate with folks on a blog. That being said, I'm smart enough to realize that I don't know everything and look for advice when I think I need it. That doesn't mean I want or expect every know-it-all smart ass who can't handle reality and lives vicariously through blog posts to get on here and be condescending. Hurt feelings you say? Not hurt feelings, now I'm just calling it like 'I' see it. You guys clearly have no helpful advice so after these posts today, saying my peace, I'm done on here. I can figure this out on my own reading other posts.

Last but not least and for anyone else who may stumble upon this in the future (because I believe the purpose of these posts is to be helpful), I did figure out that the rough start was caused by an unseated PCV valve. Long story short, when I removed/replaced the earlier one I cracked the pcv seat of the plastic valve cover. Since the new one already had a new PCV valve installed, I didn't bother to make sure it was fully seated. It was not and had worked it's way fully unseated. So that problem's solved.

Bon Voyage!
The very nature of posting on a forum about an issue invites responses that you won't agree with. And apparently your feeling were hurt as you responded in a negative fashion trying to bolster your argument, so you still need to get over yourself in this respect.

You found a solution to your issue, which is great. However, you still have many unknowns as I've highlighted before.

Will your engine last or not can only be solved by time. If you're correct, then great, if @rich6700 and I are correct, well then you'll be spending more money. Either way, it doesn't really matter to me.

Anyway, as before, I wish you good luck with this... :beer:
 

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LOL, you have no idea what my background is and what experience or knowledge I have. Thank you for making assumptions and making an ass out of yourself. There are two types of people on these blogs; those who live on here, and those who come here with questions. I fall into the latter and don't have a problem saying it. You really should learn grammar before you start being a condescending smart ass so that when people read these posts in the future they think you at least graduated high school before offering your brilliant advice. And last but not least, I have asked questions before, ahead of time, and I get the same type of replies from smart asses like yourself who have nothing meaningful to contribute but just want to stroke your own ego and belittle people. I'm happy where I am in life and don't need to put people down for asking questions, how about you? The mechanics that I've been around usually like to teach people the trade, not belittle people for asking questions. Have a nice life.
You dont know my background either. And this is how you teach someone a lesson. Old school way, not by coddling them and being nice. I was most likely working on vehichles before you where born. And in all of those years I have never pulled an engine apart the way you have looking for a problem. I would have reccondmended other diagnostic procedures to do first before pulling the heads and pistons out. Like a compression test, leak down test, fuel pressure test. But you made no mention of doing that. So when someone else has this problem and they do a search and find this thread they'll no what not to do.
Now don't you feel better, everybody learnt a lesson today.

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