So, after 7 weeks in the shop, my well regarded Chevy service guy finally found a broken valve spring as the cause of my intermittent engine misfires and CEL P0300 ( random misfires.)
I recall many internet discussions about weak/broken valve springs in Corvettes but most, if not all concerned the LS engines. Is this an issue with the LT1?
They first thought it was carbon build up and a bad injector, so they chemically cleaned the intake valves and replaced one bad injector in #2 cyl. Better but No joy!
After consulting GM engineering they did some more diagnosis and decided it was electrical problem with the ECM which they replaced under warranty. Ran good for 2 days then got even worse!
Now they started to go back over everything and they found a broken valve spring #2 cyl.
Scoped the cylinder and said it looks just fine, so they will replace the broken spring and expect all to be well.
So was the problem a weak spring that finally gave up, or something else?
Assuming the random misfires disappear, I am concerned about possible collateral damage: bent valve, damaged valve
seat ,worn / bent valve guides?
I would feel better with a compression/leakdown to determine the health of the engine, especially the #2 cyl. Am I being unreasonable?
Car has 38000 miles so only the Drivetrain warranty applies.

 

I think you're expectations are very reasonable. Hopefully they are planning to do a compression or leak down test, but would request it if they aren't planning to do so. It's a simple enough test to provide some assurance that all is good.

 

It probably wouldn't hurt to have them change all of the valve springs.

 

At 80,000 miles, the valve spring in cyl #8 broke.

Shut it down almost immediately (I had to move out of the way of an ambulance--timing is everything ), and had it towed to my guys at the local Buick/GMC dealer. Replaced and on the road in a couple of days. Fortunately, no other damage. It was covered on my drivetrain warranty.

Three weeks later I drove it solo to Texas and back (5,000 miles total), and it's been fine for the last ten thousand.

 

Thanks, that's good to know and encouraging. In just 4 weeks, I will be leaving on a 5400 mile drive to Montana and then back through the Michigan upper peninsula with a first time ever stop at road america just for some parade laps.

 

atl 3200 miles I experienced a broken valve spring (it worried the **** out at the time it occurred). a year an half later (only additional 3200 miles) I haven't experience any related problems

 

That might be the correct thing to do. There may have been a bad single spring or there may have been a bad lot of springs. As for collateral damage I doubt you have it as if you had it your symptoms would be a lot worse than a few misfires.

Bill

 

You guys are all lucky ... at 32,000 miles I dropped a valve at 70 mph before I could get it pulled over the engine just ate itself to pieces

Dealer was great , found a broken valve spring which popped the retainer and caused the valve to drop into the motor and wreak havaco 10 business days later the good news is I have a brand new motor in my 2015 ... the bad news is I have a brand new motor in a Corvette... oh well I plan on driving this one forever so it will never be a pebble beach 100 point car anyway

Dave

ps I have two friends that also dropped valves in LT1's

 

 

Please explain how this was possible.

 

 

Some of your questions were good ones.If the piston never hit the valve you're all set with just the spring.That's probably why it was scoped to look for marks on the piston.
The spring obviously stayed intact enough not to lose the valve keeper.
Good luck with getting the dealer to replace all the springs.I think that would have to happen with another broken spring.

 

yup probably only do that one. What are they replacing the bad one with, another just like it? Broken springs seem to have been an issue for many years.
Would like to think if you speak to the tech and throw a few bux his way he would install all new ones, not sure they would warranty aftermarket springs though.
Most times a broken spring causes no other damage, same with bent pushrods

 

It all depends on when and where it breaks and how fast you can shut it down because it's not "if" the retainer is going to let loose it is just "when" . He was really lucky that it ran all that time
I would also stop using that dealer who was just firing the parts canon at the car instead of diagnosing ... if they just used a MDI device they would have seen that it was nothing electrical or fuel injector related ..... running rough hmmm nothing electrical or fuel related hmmmmmm simple compression test or vacuum gauge would have shown the broken valve spring ...
Dave

 

I would also stop using that dealer who was just firing the parts canon at the car instead of diagnosing ... if they just used a MDI device they would have seen that it was nothing electrical or fuel injector related ..... running rough hmmm nothing electrical or fuel related hmmmmmm simple compression test or vacuum gauge would have shown the broken valve spring ...
Dave[/QUOTE]

I'm definitely disappointed in the Service tech. He has a very good reputation and the dealer has sponsored the local Corvette club for many years. I've always been treated well there I asked for compression/leakdown at several points along the way but while they didn't disagree, they seemed to just follow the guidance from the GM engineers via phone.
I think the valve broke on startup at the dealer. They said it was running fine after installing the new ECM but wanted to get a cold start up in the morning to be sure. Tech started it and ran it up to temp and all was well. Came back much later and it barely started.
Now waiting for them to replace the brkn spring.

 

 

A thousand! Holy smokes

 

Any collateral damage will result in misfires anyway, so as long as the check engine light is out, and stays out, then you are in the clear.

 

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Indeed. Since Ken is our resident zombie hunter We have to award him this patch!