Hi Everyone! Follow up post from my previous summer one. Last summer my 2006 3.9L Monte Carlo Lt with 195,000 miles had a strange problem. The shortened summary: I had filled it with gas (it was a torrential downpour, but the station was definitely fully covered). I parked it overnight, took it about 20 miles on the highway, and right when I was pulling off the exit ramp, it seemed to fully lose power. On the highway, it couldn’t have ran any better, seemed as if it was the day it came off the lot. I initially thought the transmission had died, but when I tried to restart it, it was making a terrible noise, and kept shutting off. Well, I finally had time to take it all apart, and the pictures show what I found. The one cylinder and piston are completely destroyed, and the one next to it has some pitting going on. The one spark plug was also all bent out of shape (no picture of that). So here’s where I’m at with this. Does anyone have any guesses to what can do this? I keep thinking bad gas maybe causing detonation? Just a failed head gasket (I didn’t think that would make the piston look like this)? The change in speed and RPMs made the timing jump? Or could it have just fallen apart because of the mileage? I keep saying the highway driving appeared perfect, and it was right on the exit ramp when this happened. The air filter doesn’t look damaged, so I don’t think anything from the road was pulled up (plus 2 cylinders have damage), but who knows, maybe that’s a possibility. I can look for a new engine and swap it out (the engine was pulled 50K miles ago for a cam replacement), but I’m a little reluctant to given the sequence of events (no warning signs at all). So any ideas to what might have happened would be great! Bad gas is still my leading theory, but I don’t know. Thanks in advance!
Left with heavy damage, middle with pitting, end is fine.

Piston on right with damage, middle some damage (picture was taken backwards).

 

I'd think detonation / running lean. Wow, that's really tore up!

Any codes before it happened?

 

Before the last run, nothing other than the occasional P0118 "Engine hot ac off"(it really never had any pending or logged codes, other than when the camshaft broke). When it initially happened, it had P0106. After a few attempted starts it eventually threw p0300 (I thought that would've shown up immediately). But driving on the highway, it appeared to be as good as it could be. I mean, I wasn't watching if anything was out of whack, but it didn't appear to be misfiring (I've been in the car on the highway with a misfire, if this was, it was very hidden), and it certainly was accelerating good until the ramp. I literally went to accelerate after going around a curve of the exit ramp and the car wouldn't move, and I thought it was the transmission. Then I realized it wasn't steering, the brakes didn't work, and it was on but not running, and made a terrible noise when I tried to turn it back on. After trying the alternator, ignition switch, and battery, I checked the compression, and found in the very last cylinder 0 and a bent spark plug. I knew it had to be bad, but only got around to digging deeper into the problem This is beyond a diagnosis that I can do, just it seemed like there would be some sort of warning sign. I'm just trying to get some sort of idea as to what may have happened before I either put a new engine in, or move on.

 

From the photos, it looks foreign metal objects were introduced into the cylinders. If metal entered the system after the mass air flow, it would be sucked into the individual cylinders. Another possibility is that If the wrong length spark plugs were installed. They could have struck the piston tops, disintergrated and entered the combustion chamber.

 

The metal objects is a good idea, but I don't know if it could've really gotten into the engine. The filter didn't have any apparent rips (I'm not sure if the rips would be obvious), and nothing was taken apart where something could've fallen in (though maybe I'm just overlooking something). Although, a year before, I did check the compression, but I think if something fell in at that point, it would've shown up sooner. The spark plugs have been in there for 50K miles, so I think I can rule those out (unless they somehow got deformed in there).

 

Well at almost 200K miles things wear out, although I don't see any reason it let go. If it were a head gasket it would look different. I thought you had broken a valve but they appear intact. Possibly a timing issue. Hopefully you don't run that E-85 crap in it. Just be glad you got that far, and you have a Chevy. You can get a crate motor pretty reasonable, or just a boneyard motor. There are plenty around. As far as lubrication, use a good high mileage oil such as Valvoline, Pennzoil, etc. and a good filter. I have always run Lucas injector cleaner to keep fuel from puddling due to dirty injectors. before you put a long block in have them flowed. Sadly, there are so many Monte Carlos around on the cheap you can just about buy another one for what you will pay for a motor.

 

No E85, unless the station screwed up their storage tanks. But what you said about the injectors gave me another possible theory. Assuming the piston ring is still intact, something caused the one cylinder to be destroyed, and the one next to it to start to be damaged. I'll need to remove the other head to be sure nothing is damaged there, but there is at least 1 cylinder showing no damage. Just a theory (not sure if it's even plausible), but maybe the one injector stopped working for whatever reason (clogged, electric fault of some kind), not enough gas went in, and caused detonation for awhile (possibly in both cylinders), and maybe caused detonation pre ignition in the cylinder with the severe damage? It definitely would count as a sudden problem (no obvious warning sign), and not all cylinders were damaged. Could debris from the one cylinder be pulled backwards and go into the other? It may mean nothing, but for a while, I always complained about a low idle shake. When the car was at red lights with no accessories on, it would always keep a steady idle BUT shake, and no one could find anything wrong. Maybe that was actually a problem with the injector, firing, but maybe just not enough at low rpms, and this has been building up to the point where it finally broke. I'm kind of leaning towards the injector, but I need to do more research to see.
And send one of the ones by you over to me! I've been searching on and off for the past few months, and NOTHING has shown up here, just the occasional Impala. The guy around the block had his totaled, and gave up on selling it and donated it less than 2 weeks before this initially happened, otherwise that engine would have been in mine now.

 

It's a red flag when an engine shakes. Nothing good can come from it. Either a bad coil, module, injector or timing. My last Impala had 178K and was running perfect. Faithful use of Lucas, and Valvoline. I was also not afraid to hammer it sometimes when getting on the Interstate. All I would ever see is a small white puff at higher RPMs. And yeah, when engines start self destructing, parts can start swapping cylinders. I bit the bullet on my 2000 Blazer, and put a guaranteed reman in for $5500. This included new everything, like belts, hoses, etc. It also came with a 5 year, unlimited mileage warranty that covered parts and labor. Expensive, but I bought this Blazer to keep, and now I have real peace of mind. I have made up my mind to now buy anything newer than a 2012. The factory is throwing so much crap on these cars now trying to squeeze every mile out of a drop of gas that it is a PITA with all the sensors involved. I cannot ever remember either of my Malibu's failing me, and one had 245K miles on it. The one now has 138K and runs perfect. My MC went through the typical 3.8 problems with oil pan leaks, and intake manifold problems, but runs like a raped ape. I think they devalue the HP on these SC motors. Strongest 240 HP I have ever driven.

Back to your issues. Best investment I ever made was a GM plug in sensor I got from Ebay for $12. You can download Torqlite app for free, and always know (for the most part) what is going on. The only code I hate is the EVAP, which can be a variety of things, and only seems to flare up during cold weather. You can also clear codes with your phone. Best money I ever spent. While your motor is down, I would go have the injectors flowed. That should tell you what is going on. There is a really good Youtube video about some guys buying a 928 Porsche for $500 and turns out all that was wrong with it was injectors. Oher cars have been bought that didn't run and it was crank trigger sensor. Doesn't take much these days for them to start having problems with all the sensors. My 2014 Malibu ran great, but kept flashing error codes. I ended up spending $1700 at the dealer to get them sorted out. This is car that ran to Indy and back from Nashville with no problems. Makes you want to scream sometimes.

 

Yeah, the shaking didn’t make sense, but no one could come up with anything. And I didn’t have much faith in the guy who charged $300 to clean the throttle body and IAC valve (which it turns out this model doesn’t have). It would be something if it was minor detonation going on all along. I found that if I kept the fan slightly on, and the vents closed, the RPMs would be slightly higher and the shake would stop, so that’s been the fix for I don’t even know how long, maybe the last 100k miles (something insane like that). And when you describe the reman engine like that, the expense is totally worth it (the guy down the road wanted only 1K OBO, but who knows how long it would go, just it was working when it was totaled).

I was completely unfamiliar with flowing injectors before, I just looked into it a little and will definitely do that if I end up rebuilding. I wonder if one of the cheaper cleaning machines would work good enough, they look like a fun addition to the tool collection! And yes, I have one of the cheap Bluetooth scanners (an HPtuner is on the to buy list for the crank relearn if I go that route).. that thing has helped me out who knows how many times, everyone should have one! I tried to go through all of the functions on it, but have only scratched the surface. Reading logged and pending codes, and the readiness monitors was good enough, but maybe it could help more in this case.