Another broken valve spring! 2014 Sierra 6.2l

B14Sierra · July 17, 2019

Ok, so here is the story. Sorry in advance for the long post. At about 60K was on a road trip I was going about 75 took it off cruise control and truck skipped and then flashing light and TC light on. Started running rough and pulled over to nearest gas station. No matter what I did the truck would barely start and barely idle, ticking and missing like crazy. Under warranty, get it towed and 3 days later because it happened on a Saturday broken valve spring and on my way. Around 30K later I'm driving and all of sudden light flashing and TC again. No stumble or warning besides lights. It seemed smooth at higher speed. I get it home and check all the wires. So, because it happened before pull the covers. Everything looks ok running. No bad lifters and no noise. Had the coils plugged in so couldn't really get a detailed look at everything. I change the plugs and wires still the same. Buddy brings me a cheap code reader and get the P0300 code random missfire. That is all that would come up. Like I couldn't tell that already. lol. After a few attempts with reader I finally get a P03005 code. Cylinder 5. I swap coil packs and same code. Now this code only came up twice and would go away no other code, so I cross out coil. What's left? Injectors right. I should have gotten a better code reader because I replace all 8 injectors. After this, now I start getting all intake codes from the MAF, TPS, and MAP and again Cylinder 5. So, now I'm like what is the last step? Has to be a valve. Sure enough, pull the valve cover really get down and look. Broken intake spring. At first I was thinking just replacing one but I think I'm doing them all. I don't trust this truck anymore. I've driven nothing but GM my whole life but this one has put a sour taste in my mouth.

B14Sierra · July 18, 2019

Just wanted to share what I've found. After taking the broken valve spring out I was looking over the others. I think I know why this is happening. The springs sit low in the head so there is a machined area around it like a pocket to provide space for the springs. Looking down the springs I noticed most of them have a gap between the spring and head. I found one tonight that is super close and looks like it could make contact. Eventually I see it rubbing through the spring. No shavings, marks on the spring I can see at this point. I think as the spring gets weaker or it wasn't truly round, or placed in wrong from the factory. I think it could rub up on the head surface at some point and break. I'm not 100% sure that is what is going on but it doesn't look right.

B14Sierra · July 18, 2019

After closer inspection I think that other spring in question is broke too! See how close the springs are from the head?

B14Sierra · July 18, 2019

One on the left is the one replaced at 60K. You can tell because of blue paint. Intake side. One on the right I think is now broke which is exhaust #3, along with intake cylinder #5.