Car falls on face right at 6100 rpm

[kinger]

It also blows some sort of grey cloud when it does it.  I have no idea what started this, I regularly run it hard to 5500-6K then shift as its worthless over 6200 but this is new, its like its hitting the rev limit.  Works fine below this, really bizarre.  I am wondering if I am floating the valves or something. 

Any ideas?  I got a log and nothing looks bad at all, good fuel pressure, MAP, Spark, etc.  Nothing shows up. 

Thanks

[FC3S Murray]

I just experienced this on a customer's 2010 SS Camaro.


Ended up being a #1 exhaust valve being busted. He had dual valve springs thankfully. The previous tuner had disabled any misfire detection.


Would pull strong until about 5300 rpm and fall flat on its face.

[kinger]

It sure feels mechanical although I have never had a motor like this but if I had to guess I am thinking valve spring as well.  Time to pop the valve covers off. 

I disconnected my Racelogic TCS just to make sure that wasn't it and its not, just funny its exactly at 6100; in my logs like at 6108 I am lifting on the throttle on the 4 times I captured it.  I was hoping for a easy non-mechanical fix ha! 

I won't run it up there anymore until I figure it out.  These are patriot heads from back in the day and I think have crane dual valve springs, so not very high quality to start with, old, and have about 25-30k miles on them at .585 lift. 

I have my new 434 being built so I will try to limp this by until its swap time. 

[spacevomit]

Aren't there like, harmonic events that happen at certain RPMs? It could be the second harmonic vibrating the shit out of the busted piece.

[FC3S Murray]

Any update? Was it a valve spring?

[kinger]

No update, I was going to pull a valve cover but I got busy and worked on my farm land instead.  I did it one more time, as I saw my fuel pressure dip and was hoping maybe the summit racing fuel filter Lane installed a decade ago was maybe getting tired but it was still 55+ psi so I don't think a 2 psi dip would cause it to hit so hard. 

I did give it a good look over to check for obvious stuff and all looked normal.  So I pretty much have to start pulling it apart now.  It runs great up to that so I may just skip it all and when I pull the motor for my new 434/mamo beast this winter I may take it apart as a learning opportunity.  I keep thinking it needs to be in a boosted application, all forged low CR, and aluminum block.  Would make a dang nice 800whp engine in something else that I care less about then my RX7.  I want the RX to be high dollar, reliable, and perfect if I can.  I am getting in the mood to hot rod something I care less about like an RX8 or something.  I will follow up if I find it. 

[MPbdy]

That would make a good boosted motor.  Probably re-ring it with a little bigger gap and a fresh hone on the cylinder walls would get you there.

I wouldn't keep running it until you figure out what is wrong.  Would really hurt to drop a valve.

What is the MAP doing at say 5500 rpm vs 6100 when it is stuck?  Can you compare MAP values from before it had the problem?

[flattop]

don't know if this is helpful or not....some time ago when I was changing my rev limit (fuel cut) settings, I would get random fuel cuts during WOT but below the value I was setting.  I believe the fuel cut settings for each gear are not settable.  HP Tuners does not recognize which gear my (LS2) car is in.  I believe this is due to having no BCM wired in with the tranny and ECM.  If I recall correctly, the remedy was just to set all rev limits to the same rpm.

[kinger]

That would make a good boosted motor.  Probably re-ring it with a little bigger gap and a fresh hone on the cylinder walls would get you there.

I wouldn't keep running it until you figure out what is wrong.  Would really hurt to drop a valve.

What is the MAP doing at say 5500 rpm vs 6100 when it is stuck?  Can you compare MAP values from before it had the problem?

Yes agree, I think for very little actual parts I could blueprint the current motor and make a dang nice boost motor. 

I do have dual valve springs so can't really drop a valve but I have stopped running it for a bit. 

Map looks normal 95-97 kPa and stays there until I let off the throttle.  Nothing shows up in the logs.  I just need to pop the valve cover but I'm just stalling, been busy with other stuff and with the 434 being built, I can't say that I care to much about this one until its out and maybe then I do a more detialed teardown investigation.

[kinger]

don't know if this is helpful or not....some time ago when I was changing my rev limit (fuel cut) settings, I would get random fuel cuts during WOT but below the value I was setting.  I believe the fuel cut settings for each gear are not settable.  HP Tuners does not recognize which gear my (LS2) car is in.  I believe this is due to having no BCM wired in with the tranny and ECM.  If I recall correctly, the remedy was just to set all rev limits to the same rpm.

Thanks for that, I went in and all my rev limts are set to 9000 by gear.  Have been forever.  I did however have my traction control set up with rev limits recently hooked back up so I thought that could be the cuplprit, so I bypassed the injectors and its still doing it.  So I don't 'think' its electrical.  We shall see.  Probably should pull plugs too while I am at it. 

[kinger]

Started with the obvious, and found something interesting.

Last year I lost a TB screw and thought the motor ate it. 

I looked in the intake and look at what I see! 





That’s good the motor didn’t eat it!! 

My filter has never been cleaned. I’m not sure that’s causing my issue but time to clean its for sure. 





I’m also toying with removing the cat and looking at it. 

Valve cover job won’t be fast so I’m putting it off lol. I did listen really close and I found no odd noises at idle or revving from the valvetrain.  I would think a broken valve spring would clunk around a bit. 

I’ll keep digging in.


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[FC3S Murray]

OMG.....that filter

Get the valve cover off ASAP.

[Gunnytron]

Lucky find on that screw, and yeah, that filter is manky.

[kinger]

Pulled valve covers and all looks normal, although not sure how I would see a broken inner spring anyway.  Checked all the rollers, nothing loose or bent, clean oil, not sure if I can do anymore until I pull the valve springs out of it. 

Any other suggestions?









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[FC3S Murray]

Do you show any misfires while data logging?