23 C8 Engine Knocking Problem
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 27
Likes: 19
From: NYC
23 C8 Engine Knocking Problem
Hey, 2023 HTC
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
Pro
Joined: Nov 2017
Posts: 713
Likes: 506
Hey, 2023 HTC
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
Quite likely normal, and more so with the LT2. LT1 and LT4 do it in the C7 and the Camaro. Do you hear any metallic ticking or knocking? If you have a metallic tick or knock, there's an internal engine issue.
There is a bulletin for 2020-2021 that would still apply to 22 and 23. 21-NA-123: Rough Idle with Misfire Counts on Random Cylinders, Malfunction Indicator Lamp (MIL) Illuminated - (Jun 29, 2021)
Technically its about possibly getting a CEL for misfires, but has a good explanation on this engine and how its designed to run.
This condition may be caused by marshalling the vehicle around and/or short runtime soot, fouling the spark plugs.
- The LT2 engine in the Corvette is a very capable and powerful powerplant, the jewel within the all-new mid-engine design. Producing 495 horsepower at 6450 rpm and 470 lb-ft. of torque at 5150 rpm with performance exhaust, this engine produces more naturally aspirated HP per liter of displacement than any Corvette engine in history.
- To fully enable this extreme level of engine performance, the LT2 was designed to be driven. Like many performance car engines, the LT2 is sensitive to short run-time starts where the spark plug does not have time to heat up. In these cases, carbon from the combustion process can accumulate on the spark plug and result in rough idle or misfire. The best way to keep your spark plugs clean is to safely exercise your Corvette on your favorite roads or track. Both running your engine and spirited driving can clean plugs that may be partially impacted.
- Whenever possible, try to run the engine until it has reached a coolant temperature greater than 51°C (125°F), and/or at least 3 minutes of engine run time, instead of frequent, short duration start/stop cycles.
Safety Car
Joined: Nov 2021
Posts: 4,309
Likes: 3,830
From: Northern Illinois
Hey, 2023 HTC
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 35,106
Likes: 12,446
From: NE South Carolina
Hey, 2023 HTC
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
For the past 2-3 weeks or so, I’ve been experiencing some symptoms like engine knocking. It won’t really make a sound, but when still (parked or brake, doesn’t matter) the engine will jolt inconsistently (sometimes every 1-2 seconds, sometimes it goes 5-10 seconds without). Not noticeable while driving.
It feels like a thumping that shakes the cabin, not violently but enough to be noticeable. Everything shakes. Fill it up with 93 at a BP, don’t think it’s an octane issue. Kind of concerning, have drove it til empty and refueled and still have the issue. Will probably take it back to the dealer soon, but wanted opinions.
Especially since you different a difference.
Last edited by JerryU; Nov 9, 2022 at 05:33 PM.
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I would just get the dealer to take a look at it - if any codes are set, their scan tool can quickly identify the source.
Safety Car
Joined: Jul 2013
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From: Granada Hills CA
Thread Starter
Intermediate
Joined: Dec 2021
Posts: 27
Likes: 19
From: NYC
Quite likely normal, and more so with the LT2. LT1 and LT4 do it in the C7 and the Camaro. Do you hear any metallic ticking or knocking? If you have a metallic tick or knock, there's an internal engine issue.
There is a bulletin for 2020-2021 that would still apply to 22 and 23. 21-NA-123: Rough Idle with Misfire Counts on Random Cylinders, Malfunction Indicator Lamp (MIL) Illuminated - (Jun 29, 2021)
Technically its about possibly getting a CEL for misfires, but has a good explanation on this engine and how its designed to run.
So TLDR, GM made the LT2 a "hot" engine. In doing so, it needs a good ol Italian tune up to keep the plugs clean. We've had two C8s come in with misfire conditions and we found out that the owners of both of the cars would start the car once a month to "keep the battery charged". One car came in running on all of 3 or 4 cylinders, it was HARD misfiring. 8 new plugs and it was like nothing happened to it.
There is a bulletin for 2020-2021 that would still apply to 22 and 23. 21-NA-123: Rough Idle with Misfire Counts on Random Cylinders, Malfunction Indicator Lamp (MIL) Illuminated - (Jun 29, 2021)
Technically its about possibly getting a CEL for misfires, but has a good explanation on this engine and how its designed to run.
So TLDR, GM made the LT2 a "hot" engine. In doing so, it needs a good ol Italian tune up to keep the plugs clean. We've had two C8s come in with misfire conditions and we found out that the owners of both of the cars would start the car once a month to "keep the battery charged". One car came in running on all of 3 or 4 cylinders, it was HARD misfiring. 8 new plugs and it was like nothing happened to it.
Doesn't sound like a knock to me. It may be a miss or stubble on one cylinder. Could be caused by loose ignition wire (they have been reported) possibly a clogged injector not spraying properly. Since not noticeable when driving, the dealer will check to see if an internal code is being set.
Especially since you different a difference.
Especially since you different a difference.
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From: Goodyear AZ
To the op, keep this in mind if dealer can't figure it out, took me a few visits and lots of tests and GM getting involved. Timing was being thrown off 1 to 2 degrees. Good luck.
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