I have a friend with a Sky Redline, same LNF as in my cobalt. He's done quite a few performance modifications but has encountered a bit of a roadblock. Well.... actually it's more of a brick wall. Anyway, He's got forged rods, wisco pistons, arp head studs, 78lb valve springs. He's had his stock turbo enlarged to support a bigger wheel. Intercooler piping, greddy blow off valve, cold air intake, and a magnaflow exhaust system. He's also got a tuner from HP tuners and does some custom tuning. The problem is that a while back he ran too much boost through the stock engine (after the turbo upgrade but before the forged internals) and the piston rings expanded and cracked pieces out of his pistons. The car currently has everything done to it listed above but now makes an awful ratcheting noise when you start it up until it's to full operating temperature. A local shop owner has been working on it but we're all a bit lost as to what to do. It seems to have something to do with the timing chain tensioner and what not because if I'm not mistaken that's controlled by oil pressure. We tried various weights of oils and different weights seem to make the issue better and worse but it never goes completely away. I'm attaching a link to a video I took of the car making the noise. Part way through the video he blips the throttle to get the car to idle down. The car is nearly undrivable until it is up to temperature because the you can't let the RPM's get above a certain level or the ratcheting will become so bad that the car stalls and can only be restarted if the car is re-flashed using the tuner. Once it's up to operating temp it runs perfect. Also, from the video you'll notice that the water pump sounds a bit sick. We've concluded that this is due to running a higher redline and the fact that the water pump has some sort of plastic baring in it that isn't designed for that kind of RPM and is now slipping or something. Anyway, any ideas would be great... here's the link.

YouTube - IMG 0404

 

Wow, no clue, but in for the results.

 

sounds like a dropped valve to me. but id have to diag it myself.

 

What exactly is a dropped valve? If it were a dropped valve would it stop after the car is warmed up?

 

Sounds more like the valve train as opposed to a timing chain. A bad spring, maybe, but the motor should be taken down to make sure. The ticking sounds like a bad lifter would on a V-8 almost.

 

a dropped valve doesnt have to mean like it is litterally in the cyclinder just free, what i am meaning is it could be a valve that was over reved and it eased its way out a little bit and now it contacts with the piston. but id have to diag it my self.

 

its fast enough to be in time with the three lobed cam driven hpfp...and based purely on operating temperature conditions I'm under the assumption there is something wrong with it. Any logs I can see, particularly looking at the cam angles, temps and fuel pressure.

 

The sounds I'm hearing are in time with the high pressure fuel system as well. Both the injectors and the high pressure pump.

Since the intake manifold was removed, was the sound insulator around the injectors reinstalled? If not that'd make the clicking of the fuel injectors MUCH louder than normal. Which is what this sounds like it is. Also, if you unplug the high pressure pump and start the engine, some of the noise should be eliminated. You'll set a code and be in reduced engine power mode so be sure to clear that after reconnecting everything.

That just sounds like un-muffled injectors and normal operation of the high pressure fuel system to me. Its too light and high in pitch to be a lifter.

 

How exactly does a spring go bad? Would that just be like one of the springs doesn't apply the same pressure as the others. Also I should be able to get some logs just give me a day or two. As far as the dropped valve thing goes, I thought the LNF pistons were contoured so that they can't actually hit the valves or am I mistaken?

 

im seconding the thought the sound deadening material is missing.

 

Would the lack of sound deadening material really cause the engine to stall and refuse to restart without flashing? Somehow I just have a hard time believing that's the case. I'm thinking you're talking about the foam type stuff that is wrapped around the block.... something I've noticed is somewhat in the way when I try to get to my oil filter out on my cobalt? Just trying to get an idea of whether we're thinking of the same thing.

 

improperly tuned maf relocation causes trims to skew beyond 20% which WILL make the car do all kinds of bad things.

 

As far as I know the MAF hasn't moved from it's stock location. It has the same issues with the stock GMS1 tune as well as custom tunes. I don't really see how it could be an issue with the tune because no matter how the car is tuned it still does it.

 

who is tuning it?

If I was you I would send a log to a good tuner.

 

Well with regards to who's tuning it, that'd be GM as far as GMS1 goes. Now we've modified air load tables and fuel mixtures a bit but the point here is that it worked perfectly before the forged rods, wisco pistons, and 78lb valve springs on the current tune and on the GMS1. Now it does not work properly. Seeing as how the only things that have changed are not related to the tune that leads me away from the tune. Unless you're suggesting that the car needs to be specifically turned to handle the new parts. In which case why does the issue go away when the engine is up to temperature. We're going to do some logging and get the error code it throws when it stalls here in a day or two and I'll report back.

 

If you didn't relocate the MAF when the BOV was installed that could cause the fuel trims to go completely haywire and cause a stall.

Since the cat warmup cycle is appearently still enabled, the turbo does spool up some on a cold start. This could force your metered air out through the BOV.

 

Well, I know that's not happening because we have the BOV adjusted to be about as stiff as it gets as far as how much pressure there has to be to open it. Also, the BOV was in place before the rods, pistons and valve springs and had no issues what so ever. We did the rigging to apply positive pressure to the recirculating BOV that is on the turbo when we first installed the aftermarket BOV so it isn't opening either.

 

Was the timing chain tensioner installed properly? It should be compressed and locked, then installed and released. If it is not seated on the chain correctly, it will be noisy. If it is stuck compressed, it will be noisy. Something to check...

 

Not enough oil on it, too much compression, too much lift, too high of rpms, bad batch of springs, not seated properly, or a host of other things. I would check what Matt at ZZP said first that would be the easiest. But if it is not that then check the valves, cams and springs. From the video, which is obviously on youtube and will not allwo us to diagnose it like we are right there, it just sounds like a valve issue. I have messed with alot of V-8s and that is the sound the make when valve lash or a lifter is out of whack. But this darn motor makes so many ticking noises its hard to tell really.

 

i would lean away from valvetrain issues as the tempo of this seems WAAY to fast to be a single cylinder/spring/valve etc. The chain seems more likely.

 

Do you work for ZZP? Would you guys be willing to work on it even though it's a Sky and not a cobalt? We're really out of options on people that know anything about an LNF around here.

 

hmmm, sounds to me as though all to bases are covered here;

the high pressure fuel pump initially didn't have the insulator, and there was a recall for the early LNF Solstice's & Sky's to have that installed ~ so that is a good idea...

but assuming that's not the issue, I'd start off easy;
remove the blow off valve, and put the tune back to stock GMS1 ~ if the running issue goes away then you know it's all in the tune & BOV setup;
if it persists, I'd be inclined to pull the engine to pour over it ~ have you looked at the Exhaust temps for each port? ~ if the numbers seem off on one or two ports, it could indicate valves that are no longer seating properly ~ it's easy to miss this as you cannot always eyeball if they are ok.

 

When I listened to it I thought chain tensioner problem. Never heard it on an LNF first hand though.

 

It sounds like cam phaser rattle that LNF get on cold start up every once in awhile but only last a second or two, not minutes like yours.

 

Yes, I did notice a striking resemblance to the quick rattle I get now and then in the cold. I'm wondering if something isn't going on with the cam phasers and the stiffer valve springs not getting along properly. I have a very rough understanding of how all that works. I do know that something actually broke on the mechanism that controls the cam position. What ever broke was fixed but I think something is wrong with something regarding that system.