Originally Posted by Gavin Costigan

Thanks. I appreciate the input. I usually examine the oil every oil change and never noticed any metal flakes or anything out of the ordinary. The oil pressure has always been good too. I know what rod knock sounds like. This is definitely not rod knock.

As for the flex plate, that might be something worth looking at. My issues here with the o2 sensor and the knock all started when they replaced the transmission back in January. I would think that they’d have said something if they saw the flex plate was cracked.

I could see it being loose bolts but I don’t think it sounds quite like that, but it might be worth looking at.

another thing I’ll note is the first time I heard the noise, I found the intercooler leaked it’s coolant out. After refilling, bleeding and fixing leaks, it helped, but the knock was still there. As we’ve approached cooler weather, it seems to improve I guess from lower intake temps. That’s what makes me think it’s spark knock.

I do think it’s odd that it throws the code while the engine is fully up to operating temperature. Specifically accelerating past the rpm where the knocking is. If I do light driving and never exceed 3200rpm, the code goes away after a while, but when I drive it harder, it comes on. I read somewhere that it throws the check engine light within 60 seconds of determining a fault.

It is definitely a weird gremlin. I suspect they damaged or pinched wires whether it just happened because of age, or it was negligence. It’s going back next week to be looked at again.


Edit: I just looked at a couple of videos showing what a damaged flex plate sounds like. It seems like that only happens at low rpm rather than the midrange.

Originally Posted by H2monsta

Ok, if it sounds like that video it is most likely spark knock. Do you have a generic code reader that can display live PID data? I want to see a few things. I want to see what your LT and ST Fuel trim readings are; at idle and especially under the loaded condition when you are having the issue. I would also want to see pre-cat o2 readings, as well as MAF reading at idle and WOT. I would be looking for the MAF reading in gm/S, and at WOT I would want to see a minimum reading of 240. At idle, somewhere around 4-6. I will be honest and tell you i'm not sure how the S/C will affect what I know to be "base-level" readings.

You could have a dirty/bad MAF, it could be heavy carbon deposits on the pistons. Another possibility is something EGR related, if its not fully opening under acceleration (carbon deposits can cause this). The tubes might be clogged partially with carbon as well.


These are some more basic tests we could do with simple tools if the above turns up nothing. If you have an "advanced" scan tool, we could monitor knock as the event is occurring to make sure the knock sensors are doing their jobs and retarding timing.

Originally Posted by Gavin Costigan

Unfortunately I don’t have a live data scanner? Would that be something that I could rent from an auto parts store or somewhere, or would I just have to suck it up and pay the &150 or so to get one?

Originally Posted by H2monsta

https://www.amazon.com/Kzyee-KC301-S...ICLE_SCAN_TOOL

Here is one on sale for $55 bucks!! Well worth the investment. You are not looking for the scanner to "do" anything, just read the sensor data that the car is providing.

Originally Posted by H2monsta

Ok, if it sounds like that video it is most likely spark knock. Do you have a generic code reader that can display live PID data? I want to see a few things. I want to see what your LT and ST Fuel trim readings are; at idle and especially under the loaded condition when you are having the issue. I would also want to see pre-cat o2 readings, as well as MAF reading at idle and WOT. I would be looking for the MAF reading in gm/S, and at WOT I would want to see a minimum reading of 240. At idle, somewhere around 4-6. I will be honest and tell you i'm not sure how the S/C will affect what I know to be "base-level" readings.

You could have a dirty/bad MAF, it could be heavy carbon deposits on the pistons. Another possibility is something EGR related, if its not fully opening under acceleration (carbon deposits can cause this). The tubes might be clogged partially with carbon as well.


These are some more basic tests we could do with simple tools if the above turns up nothing. If you have an "advanced" scan tool, we could monitor knock as the event is occurring to make sure the knock sensors are doing their jobs and retarding timing.

Originally Posted by Gavin Costigan

Okay. After a busy few days. I was able to go get some data with this sorta crappy scanner. I did my best. For some reason the scanner says bank 3 instead of bank 2. Each video is a separate pull in the same location. One pull with Bank 1 stats on and the second with Bank 2 showing. I screen recorded the data replays. I only could fit 2 on screen at a time and log 4 at once, so each video is 1 log with two screen recordings of the data if that makes sense. I also synced them up along with audio from the car. I'm sure you will enjoy my commentary as well.

You'll here me say "knock" but you cant hear it at all on video. It is just a couple clacks drowned out by road noise. Again, The knock gets uncomfortably loud only when pulling a trailer. And at full throttle, when it shifts to second, the rpm is above the rpm where it knocks.

There are two "pulls" in each video. The first is just wide open throttle, the second is me shifting to second gear, going up a hill and trying to keep it at 32-3500rpm where the knock happens.

Let me know if google drive doesn't let you access them.
Idle-
https://drive.google.com/file/d/1DJa...ew?usp=sharing
Bank 1 Data(starts at 00:43)-
https://drive.google.com/file/d/1VgZ...ew?usp=sharing
Bank 2 Data(starts at 00:32)-
https://drive.google.com/file/d/1Iux...ew?usp=sharing

Originally Posted by H2monsta

So, from what I could see, everything shown looks pretty good. I would like to see the LT Fuel trims Bank 1, LT Fuel trims Bank 2, ST Fuel trims Bank 1, ST fuel trims Bank 2, all simultaneously shown as the knocking is occurring. I also want to see Engine coolant temperature, Intake air temperature sensor, Actual EGR, Commanded EGR, and EGR Error, NOx Sensor Corrected Data. I would ask for your spark/timing PID data; but Im sure they were adjusted from base level when it was tuned for the S/C.

My gut feeling tells me you have some heavy carbonization forming on the pistons and valves. You could potentially verify by pulling some plugs and sticking in a borescope. You could try to do an old school "water" cleaning by getting the engine hot and letting it sip water from the booster line. I would caution this though, I have seen a moron stick the rubber hose directly into the water and hydro-lock an engine and bend a rod.

Originally Posted by Gavin Costigan

I can do a run with all the fuel trims later today on the same hill. Then I can do another one with Coolant temp and intake temp. I dont think my cheepo scanner will do EGR data or NOx sensor data.

It could very well be carbon deposits. I'll mention that to the mechanic to take a look in the cylindars. I know GM makes a specific top engine cleaner to clean out the deposits with. Is it safe to pull the water or engine cleaner through the supercharger?

I also read that incorrect or worn plugs can cause this too. At 100k miles if the plugs are original, it is time to replace them. They may have been replaced at 60k when the supercharger was installed but I don't know for sure. I know on the h2 when you do plugs, you likely have to do wires too, and my wires are red. Is that the color the came in from the factory.