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.
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.