2015 ZL1 knock? Conclusion @ 4/27/15

[z3R0fo01]

Def take it to another dealership. Something is not right. Like you said it could be a bad pump, injectors, etc.

[Six.Two SC]

Originally Posted by angryBits

Based on this, I'm fairly certain my car is not normal and fairly certain its not a fuel issue.

I had the same problem as you on 91 octane. I added Torco and the KR was greatly reduced; under 1 degree during normal driving and very rarely, none at WOT. I can come to the conclusion that straight 91 was causing the KR. I bet 93 may have very minor KR at times as well.

[Vick415]

Originally Posted by angryBits

Lots of posts, so I'll try to summarize:



- I've already been through several tanks of gas from several Top Tier gas stations. Always 91 Oct. The issue never faltered.



- I can try torco just to rule out gas, but I don't want to rely on torco -- I want to be able to run on pump gas.



- I have talked to people with ZL1's that live in the same area, running on the same 91 pump gas with no issues.



- I have driven 3 ZL1's and mine is the only one knocking.





Based on this, I'm fairly certain my car is not normal and fairly certain its not a fuel issue.



At the moment, I'm thinking bad MAF Sensor, bad injectors, bad fuel pump... maybe something obstructing the air intake? ... Running out of ideas. I'm hoping an Oil Separator will improve the issue if its a case of oil getting into the combustion chamber, but I shouldn't need it as others are not knocking and they don't have it.



I wasn't able to find the Air/Fuel Ratio on my DashLogic. Does anyone know how to set that up? This would tell me a lot more.





Thanks

A/F is setup using auxiliary sensors provisioned by Dashlogic. These sensors are 'add-ons' - Check out Palmer website should you go this route
I must commend you on your superior 'super-hero' like hearing for even picking up these knocks well before using a device such as Dashlogic!
I am sure you are taking necessary steps to resolve the problem. In the end you will be the KR expert with ZL1's
Cheers,
-- Vick



Sent from my iPad using Tapatalk

[angryBits]

Originally Posted by Vick415

A/F is setup using auxiliary sensors provisioned by Dashlogic. These sensors are 'add-ons' - Check out Palmer website should you go this route
I must commend you on your superior 'super-hero' like hearing for even picking up these knocks well before using a device such as Dashlogic!
I am sure you are taking necessary steps to resolve the problem. In the end you will be the KR expert with ZL1's
Cheers,
-- Vick



Sent from my iPad using Tapatalk

Haha! Thanks Vick, I have pretty big ears

I think its an easy sound to get lost in general drive train and valve train noise, but once you know what you're listening for and when it occurs, its pretty easy to pick up.

Oh I also never listen to the stereo and I usually keep my windows rolled up which I think helps.

[angryBits]

Originally Posted by shinzon

Q:What is Knock Retard?
Q:What is detonation?
Q:How is knock detected?
Q:How does the PCM respond to knock ?
Q:What does the PCM do immediately after the detonation levels begin to fall?
Q:How much horsepower do I actually lose with KR?
Q:Why do I NOT want to have KR (why is it bad)?
Q:How do I know if I have KR?
Q:What is REAL KR and what is FALSE KR?
Q:What can cause FALSE KR?

I love you.

This makes a lot of sense to me -- I feel better armed for my upcoming conversation with a GM tech this afternoon.

[Six.Two SC]

Please report your findings. I'm now getting KR even with Torco.


Sent from my iPhone using Tapatalk

[angryBits]

I went back to the dealer today. They didn't even ask to see my video, they just offered to have another technician go on a drive with me. However this experience was very different from the last.

The service guy that helped me was very helpful and the technician they hooked me up with was very honest. We went for a drive and right away he heard the tick, I didn't even need to point it out. That was all he needed to hear. He said its definitely not normal and they will fix it.

Step 1 was to look and see if any bulletins or software updates were available but there were none. They said they talked to a GM Tech on the phone and they seemed to take it very seriously. They all agreed a brand new stock car with only 2k miles should not behave this way. They said the GM Tech would come down on Monday to deal with it directly.

They gave me a loaner car. I left feeling like I was well taken care of.

[cal45]

Originally Posted by angryBits

I went back to the dealer today. They didn't even ask to see my video, they just offered to have another technician go on a drive with me. However this experience was very different from the last.

The service guy that helped me was very helpful and the technician they hooked me up with was very honest. We went for a drive and right away he heard the tick, I didn't even need to point it out. That was all he needed to hear. He said its definitely not normal and they will fix it.

Step 1 was to look and see if any bulletins or software updates were available but there were none. They said they talked to a GM Tech on the phone and they seemed to take it very seriously. They all agreed a brand new stock car with only 2k miles should not behave this way. They said the GM Tech would come down on Monday to deal with it directly.

They gave me a loaner car. I left feeling like I was well taken care of.

Great to hear this....please keep us updated. My new 15 ZL1 just went over the 1500 mile mark this weekend, while it doesn't have the tick - I'm interested just in case.

[angryBits]

Originally Posted by cal45

Great to hear this....please keep us updated. My new 15 ZL1 just went over the 1500 mile mark this weekend, while it doesn't have the tick - I'm interested just in case.

Its a pretty faint tick -- i think most wouldn't hear it unless you're paranoid of noises like me.

To be safe, maybe get a OBD2 tool to check for Knock Retard -- it's a pretty handy tool to have regardless.

[hawk02]

I'm surprised no one has mentioned burst knock.

I fought varying degrees of KR at low rpm and low engine load on my ZLl until the tuner zero'd out the burst knock table.

Now the only "kicker" that it may not be burst knock is the ticking noise the OP hears. I never heard any engine knock even though the KR could on rare occasions reach as high as 7 degrees.

Anyway, just a thought...

[angryBits]

Originally Posted by hawk02

I'm surprised no one has mentioned burst knock.

I fought varying degrees of KR at low rpm and low engine load on my ZLl until the tuner zero'd out the burst knock table.

Now the only "kicker" that it may not be burst knock is the ticking noise the OP hears. I never heard any engine knock even though the KR would on rare occasions reach as high as 7 degrees.

Anyway, just a thought...

Hmmm I can't say. But its in the shop now so whatever it is, I'm sure they'll take care of it. Hopefully they keep me in the loop so I can pass on the knowledge.

[Six.Two SC]

Originally Posted by hawk02

I'm surprised no one has mentioned burst knock.

I fought varying degrees of KR at low rpm and low engine load on my ZLl until the tuner zero'd out the burst knock table.

Now the only "kicker" that it may not be burst knock is the ticking noise the OP hears. I never heard any engine knock even though the KR could on rare occasions reach as high as 7 degrees.

Anyway, just a thought...

Interesting you posted this. A couple days ago, I took a 35 mile drive and saw 7 degrees of KR according to my Torque Pro app. This is WITH a full can of Torco and 91 octane. With the exception of CAI, my car is stock. I'm confused?? Could it be the CAI causing the KR???

[DrkPhx]

I have to believe it's fuel-related. You should never hear audible knock on a bone stock ZL1. They should test the fuel for excess water or moisture. I doubt that's it, but it wouldn't hurt to make sure. I will say my car ran like crap even on 91 clear (no ethanol); stock or modded. Same goes for my friend with a CTS-V. The ZL1 runs a lot of timing at WOT and especially in the lower rpm range you mentioned; too much for 91 imo. I know that's the highest octane typically seen on the West Coast which sucks. I wonder if they throw in a service calibration to see if that helps. Curious on the outcome.

[Chrispy]

Originally Posted by Six.Two SC

Interesting you posted this. A couple days ago, I took a 35 mile drive and saw 7 degrees of KR according to my Torque Pro app. This is WITH a full can of Torco and 91 octane. With the exception of CAI, my car is stock. I'm confused?? Could it be the CAI causing the KR???

It's likely MAF scaling in the intake. I would swap back to the stock intake, do the fuse pull and retest on the same tank of fuel.

Swapping it back take's no time at all and you can quickly rule out an intake MAF scaling error throwing STRIMS/LTRIMS out of whack. With aftermarket intakes you can get transient lean spots at different loads etc. Easy swap it and check.

Cheers,
Chris