[Kev1n]

Hello everybody,

I am new to this community and hoping your pointers can help me find what is wrong with my ZL1. This past Spring I was able to fulfill my dream of 5 years to own a ZL1 1LE. It is a manual MY2019.

My car came with a bunch of cool mods and had 9,500 miles when I bought it. It now has 13,500 miles most of which were highway miles. The mods on my car were about 1,000 miles old when I bought it:

MSD spark wires
NGK spark plugs
Rotofab intake
DSX crank pully
Kooks long tube headers with green high flow cats
Borla Atak with NPP valves and carbon tips
Upgraded throttle body
ATI damper
93 octane tune

The issue:

2 weeks ago I took the car on a track for the first time and it was pulling strong like it usually does. I did notice that no lift shift did not seem to work even though I left the gas paddle floored and was abover 5,000 rpm at the time so the car ran into the rev limiter under full throttle that one time. U had never tried to use that feature before so assumed I had done simething wrong.

Other than that everything worked great at first until I got an error code for knock on bank 2 followed by an O2 sensor error (position 1/1). This lead to a huge power reduction and a bit of sputtering from the exhaust under throttle. When I cam off the track I noticed there was a little oil in the engine compartment that had been thrown at the shock tower on the passenger side and some brown looking fluid on one of the silver pipes that usually have condensed water on them on the driver's side . Nothing much but enough for me to notice. I drove the car home 80 miles and noticed that it ran fine under low throttle just cruising on the highway but was shaking itself/sputtering under heavier acceleration. So just rolled home with minimal throttle crusing at highway speed.

Also, and this is the weird thing, the car was much quieter from the exhaust even thought the flaps are wide open to the point that the intake and supercharger sounds from the front are much more noticeable now.

After reading on here that people with Kooks headers had issues with the spark wires getting too hot, I did go and replace all spark plugs with NGK ones and the MSD wires with OE-style ones from Autozone. 3 of the MSD wires indeed looked like they had gotten cooked as they were brittle. I also replaced the O2 sensor and did an oil change as it was due anyways.

At first the car had super bad idle and a blinking check engine light after I had fixed all that which I traced down to a bad battery following code C0800 and U0401 so yesterday I also replaced the battery.

Now the car idles fine and the codes are gone. There is no more sputtering under high throttle, but the car seems like it is still quieter from the exhaust while the intake and supersharger are louder than before. Power is maybe 60 to 70% of what it used to be and it sounds like a pop from the engine bay here and there when I use the auto rev matching. No codes though :s

I am wondering if there could be a pressure leak somewhere that would explain the loss of power and changes in sound but all hoses seem fine and I could not find anything that looked visually off.

Any ideas where I should look or does anybody live in Westchester county NY who knows these cars well and could take a look for me if I came by? Was hoping somebody might have a camera that allows to inspect all the crevices of the engine to find whether a hose or gasket was pushed out somewhere when I was on the track.

Thank you all for your ideas.

[SSDan]

Perhaps one of the green cats melted down and the exhaust is restricted. Just a thought.

[ctrlz]

This pattern where things were working fine, then you ran it hard (which obviously gets things hot), and then you got misfire and o2 sensor codes... This all sounds like cooked wires over the headers. Not just spark plug wires, but sensor wires in a harness.
Search around here. This is a recurring pattern. The fact that the mods are relatively new also supports the theory. I could be wrong, of course, but the data seems to add up.

[Kev1n]

Thank you both for your ideas.

For thw cats, any idea how I would best check the cats for proper flow? I assume the answer will be take the exhaust off and stick a camera into the headers?

Will look into the wires first and report back

[Trochoidal]

Did your tensioner cylinder fail? It looks wet. If it did maybe your belt is slipping, dropping boost and losing power.

[Kamero6]

Oil splashed could be blow by gases pushing oil through. Could be through the dipstick, and oil fill cap.

One cheap and easy thing you can do is get a infrared temp gun that supports exhaust temps and check the temp of each cylinder exhaust tube, they should all be the same, unless you have a problem with one or several cylinders.
Also check the cat temperatures, before and after.

If exhaust is plugged, the engine will get really hot, but you will notice that with the temp gun. Back pressure in the cylinders can also create blow by.

[Kev1n]

Hi all,

I ended up bringing the car to the Chevy dealer to have it diagnosed. They first replaced the O2 sensor which I had replaced before. The car ran fine under light loads after that but misfired badly under higher loads. So sent it back and after more diagnosis they arrived at replacing the injector on cylinder 3 which had low flow. Made sense as cylinder 3 was the one mostly misfiring.

Car still had no power after that so they checked the cats and realized they had been burnt and clogged up as a result.

With the cats fixed the car runs like crazy again and the exhaust is as loud as it used to be.

So in the end the main issue was probably that the cats on my car could not handle the temps under track conditions because of my 760hp tune as well as the spark wires that did not have the boot protectors leading them to get melted which caused this chain of events.

Thank you all for trying to help me fix it! Sorry to report that in the meantime my employer decided to send me to Europe for 3 years starting this Fall. So now that my car is perfect again, I will have to sell it :(