Bent Pushrod, Loose Rocker, Broken Valve Spring, Toasted Intake Manifold
Well at 26030miles my 2016 JG M6 had her first real problem besides a single steering rack failure prior to the recall.
Yesterday morning, cruising to work on the highway in 6th gear at about 1750-1800rpm and around 72mph my Center Display switched to "Service Stabilitrak", TCS light came on, and eventually MIL started flashing intermittently. It immediately felt like a flat, but the TPS and handling suggested otherwise. I realized the feeling of a flat was actually the engine running lumpy, and with a sluggish throttle I put it together that it was a bad misfire....great.
Like a numb-nuts I continued to drive my tractor sounding car cautiously the remaining 8.2 mostly highway miles to work while my brain processed what was going on. Stupidly my brain didn't tell me to pull over and shut the engine off. I did however have the foresight to park in a spot where I knew a flatbed could get to...so that was something. I checked the codes, and double checked with ONSTAR - P0106 for a MAP Issue, and P0300 for missfiring. Of course they told me it'd be fine to drive to the nearest service center.....eh NO!
I'd just filled up 17miles before the missfire started so was hopeful it was a bad batch of fuel, or a shot injector, or a bad MAP sensor from the oiled OTR filter.
I got a Chevy provided flatbed tow to my preferred Service Center (stupidly drove it onto and off the flatbed - very sluggish starting), and then they drove it around to a service bay.
Unfortunately for me I bit the warranty when I installed a different tune to hopefully take better advantage of my OTR intake. I then later switched the tune back to the original as I preferred that to the supposed 'custom' remote tune I'd installed. So I'm not going to bitch and moan about loosing the power train warranty. I'll man up, pay up, and not argue.
I drive like a nanny. Have hit the rev limiter about 3-4 times in it's life. Have never had a mismatched downshift or mechanical over rev, have never done a burnout or tried for a best 1/8th or 1/4 mile time. I did have a high pitched squealing sound start around 10K miles when between 4000-4500rpm. The squeal sounded like it came from the drivers side of the engine bay. The dealer never was able to find the source of the sound, but it went away around 20K miles, and I was rarely above 4000rpm to listen for it. Oil and filter have been changed every 3000miles with Mobil 1, and serviced on schedule. No other mods.
The dealer service techs confirmed today via the service advisor that Cylinder 8 has the following issues:
-Exhaust rocker arm loose, but bolt was tight,
-Pushrod was bent,
-Valve spring was broken.
-No 8 intake runner on Intake Manifold melted/failed (P0171, P0174 Lean Bank 1 and 2 Codes - codes were after valve spring and pushrod replacement and on post assembly test drive by mechanic. Mechanic did not check integrity of intake manifold when the manifold was removed to pull the head.)
They haven't performed a leak down test, nor scoped the cylinder yet or done additional diagnostics until I gave them the okay. They're talking about pulling the head. I probably won't know more on the damage till Monday.
Okay so the main concerns are damage to the piston, cylinder walls, exhaust valve, and camshaft lobes right?
Should there be any concern of additional damage from circulating crud if the camshaft is worn?
Another question I have, and my main pondering is how could this happen?!?
Could a broken exhaust valve spring alone result in a loose rocker, and bent push rod?
Or is it more likely the bearing in the rocker was toast, and the increased play resulted in the spring breaking and rod bending?
Correct me here if I'm wrong - but on these engines a tune can only effect the timing and duration of both fuel injection and spark right?
So ultimately how rich or lean, cold or hot the combustion is in that cylinder which would burn or otherwise damage the piston, valve faces, or cylinder walls. I wouldn't think a tune alone (bad or good) would result in this damage?
So thoughts please on how to handle the repairs, and make sure the service techs do the job right the first time and catch everything. I don't want to end up with additional surprises down the road, but also don't want to have to deal with a complete engine teardown or in the extreme buying a new LS3.
Well at 26030miles my 2016 JG M6 had her first real problem besides a single steering rack failure prior to the recall.
Yesterday morning, cruising to work on the highway in 6th gear at about 1750-1800rpm and around 72mph my Center Display switched to "Service Stabilitrak", TCS light came on, and eventually MIL started flashing intermittently. It immediately felt like a flat, but the TPS and handling suggested otherwise. I realized the feeling of a flat was actually the engine running lumpy, and with a sluggish throttle I put it together that it was a bad misfire....great.
Like a numb-nuts I continued to drive my tractor sounding car cautiously the remaining 8.2 mostly highway miles to work while my brain processed what was going on. Stupidly my brain didn't tell me to pull over and shut the engine off. I did however have the foresight to park in a spot where I knew a flatbed could get to...so that was something. I checked the codes, and double checked with ONSTAR - P0106 for a MAP Issue, and P0300 for missfiring. Of course they told me it'd be fine to drive to the nearest service center.....eh NO!
I'd just filled up 17miles before the missfire started so was hopeful it was a bad batch of fuel, or a shot injector, or a bad MAP sensor from the oiled OTR filter.
I got a Chevy provided flatbed tow to my preferred Service Center (stupidly drove it onto and off the flatbed - very sluggish starting), and then they drove it around to a service bay.
Unfortunately for me I bit the warranty when I installed a different tune to hopefully take better advantage of my OTR intake. I then later switched the tune back to the original as I preferred that to the supposed 'custom' remote tune I'd installed. So I'm not going to bitch and moan about loosing the power train warranty. I'll man up, pay up, and not argue.
I drive like a nanny. Have hit the rev limiter about 3-4 times in it's life. Have never had a mismatched downshift or mechanical over rev, have never done a burnout or tried for a best 1/8th or 1/4 mile time. I did have a high pitched squealing sound start around 10K miles when between 4000-4500rpm. The squeal sounded like it came from the drivers side of the engine bay. The dealer never was able to find the source of the sound, but it went away around 20K miles, and I was rarely above 4000rpm to listen for it. Oil and filter have been changed every 3000miles with Mobil 1, and serviced on schedule. No other mods.
The dealer service techs confirmed today via the service advisor that Cylinder 8 has the following issues:
-Exhaust rocker arm loose, but bolt was tight,
-Pushrod was bent,
-Valve spring was broken.
-No 8 intake runner on Intake Manifold melted/failed (P0171, P0174 Lean Bank 1 and 2 Codes - codes were after valve spring and pushrod replacement and on post assembly test drive by mechanic. Mechanic did not check integrity of intake manifold when the manifold was removed to pull the head.)
They haven't performed a leak down test, nor scoped the cylinder yet or done additional diagnostics until I gave them the okay. They're talking about pulling the head. I probably won't know more on the damage till Monday.
Okay so the main concerns are damage to the piston, cylinder walls, exhaust valve, and camshaft lobes right?
Should there be any concern of additional damage from circulating crud if the camshaft is worn?
Another question I have, and my main pondering is how could this happen?!?
Could a broken exhaust valve spring alone result in a loose rocker, and bent push rod?
Or is it more likely the bearing in the rocker was toast, and the increased play resulted in the spring breaking and rod bending?
Correct me here if I'm wrong - but on these engines a tune can only effect the timing and duration of both fuel injection and spark right?
So ultimately how rich or lean, cold or hot the combustion is in that cylinder which would burn or otherwise damage the piston, valve faces, or cylinder walls. I wouldn't think a tune alone (bad or good) would result in this damage?
So thoughts please on how to handle the repairs, and make sure the service techs do the job right the first time and catch everything. I don't want to end up with additional surprises down the road, but also don't want to have to deal with a complete engine teardown or in the extreme buying a new LS3.