John58

I'm experiencing a "Engine Knock" at low rpms on my new 2016. I've taken it back to the dealer, but they don't know anything if their is no bulletin on it from GM. I just completed the "Break In" period and had the oil change was required by the dealer last week, but the engine knock is still there, they thought it might have been the lighter weight oil from the assembly plant, causing the concern. Plus, now there is a "Puff" noise once in a while when I rev the engine at first...I never had these noticeable issue with my C6. Please advise. Thanks

savewave

John58: I really think your question would better be addressed by the Chevrolet Customer Service representatives who are active on the site, so I'm going to move this thread to C7 General Discussion and recommend that you share your question with them via PM to "Chevy Cust Svc" on the chance they don't immediately spot it.

Good luck on finding the answer.

tunaman

Be sure you're using top tier high octane (91+) fuel. Low grade, low octane gas can cause engine knocks.

Try getting a tank or two of premium from a different station, if you tend to gas up at the same station, and see if it goes away.

DCortez

I'm planning on 93 and only going lower if pushing my car to the next station is my next option.

JoesC5

GM does not put in "lighter weight" oil at the assembly plant. GM puts in 5w30 dexos 1 oil at the assembly plant just like the dealer is instructed to use during the oil changes.

Black&White

Make sure all your plug wires are tight to the plugs.

jerryv

Describing a sound is like discussing music .. not a substitute for the real thing.

A 'knock' could mean a lot of different things, based on your personal experience ... It could describe a 'ping' caused by too much load on the engine and gas with too low an octane rating .. the kind of knock you used to hear on older cars. But the Corvette is supposed to compensate for that kind of 'pre-ignition' .. unless you're really trying to push the car way too much at low rpm in too high a gear. Or a 'knock' might be from the direct injection, or it could be valve clatter or a collapsed lifter .. OR it could be something big, like a bad rod bearing ..

The best way to let us know what you're hearing is an audio recording. Failing that, describe the noise as accurately as possible, and describe the precise conditions under which you hear it ..

A dealer that can't be more helpful than that sounds as useless as t-ts on a bull.

senah

you are lucky in that you are only 20 miles from les stanford in dearborn. their service department should be able to diagnose the problem. if the noise is a light knock from the top end of the motor and you are getting a muffled cough (backfire) when you rev it, it sounds like a possible valve issue, but that is just a guess. it could also just be an injector issue. whatever, take it to a dealer that knows corvettes.

John58

Really,


The dealer is giving bad information. Why isn't the Bowling Green placing Mobil One in the engines as specified my the owner manual and the on the oil cap?

Red C8 of Jax

Mobil One being put in the C-7 at the factory has been discussed at length on this forum. Mobil One is the factory fill for the C-7's and the dealers according to GM, should use Mobil One for your free oil changes. I have a letter from GM informing the dealers to use Mobil One.

meyerweb

Actually, GM puts Mobil 1 in every Corvette at the factory. Mobil 1 does meet Dexos specs, so your post isn't technically wrong, but since most people here use Dexos to mean the GM synthetic blend, I just want to make sure it's clear.

meyerweb

As for the engine knock, are you sure you're not hearing the ticking of the Direct Injection? These high pressure fuel injectors do make a pretty loud sound, especially when the engine is cold.

1776DAVE

Pulled up to house and like normal I sat in our 16 z51 for a few moments listening to the car.
Suddenly I noticed it had a tick to it!
Not real loud, but kinda like mechanical lifters. It was less noticed with higher rpm. But returned at idling . Car had 2700 miles. It did not doit the next day or sence. If it had it would have been to shop!
But was bothered by one occurrence. Will follow this thread in case it happens to some other person.

Vetteman Jack

Could very well be what it is, but hard to say without actually hearing it.

JerryU

Have to question anything a Service Manager or Tech would say if they don't know "break-in" oil went out years ago! They should be able to check codes to see IF in fact knock was detected since the sensors should hear that faster than you and have retarded timing etc.
May be the high pressure injector noise you're hearing and from time to time there is a slight pop on start up. Get a fresh batch of quality, top tier gas of the highest octane available in your area and if you still think you hear a knock, find another dealer!

DAFFYDRUNK

The "puff" noise may be normal too. Particularly in the M7s, you hear an air gulping sound if you jab the gas a little... Or as Ross Perot once said, "that giant sucking sound". A little easier to hear in the M7 as you clutch it and free rev it.

NSC5

What you normally hear with the DI engine is the high pressure fuel pump which is very noticeable at idle and even more so if you are next to a brick or other solid wall that reflects noise back to the car. My first gas DI equipped car was a 2008 Cadillac CTS and it had a lot of sound deadening added to quiet the fuel pump "tick/click" but it was still audible at idle but it seems now that newer DI cars have less sound deadening; probably because the auto companies assume customers have grown accustomed to this new operating characteristic.

360Lemans

Two great and Factual replies to your post and no response?? Your only reply was complaining about GM and the dealer. So just what are you fishing for? You started this post (your first post to this forum) and since then you posted four other times, three of them negative!!!

Yes the LT1 sounds different than the LS3/LS2. The longer you think in a negative way the DI tick will start sounding like a loud knock

Jim Barker

Get the oil analysed , that way you fears can be put to rest. This engine is noisy compared to earlier models. This is an area the dealers could improve on. They just seem to wait until something breaks big time.

6104696

The puff noise is definitely normal for the C7. I thought it a bit odd when I first starting shopping for C7's (my two CTSV's didn't do it, nor has any other modern car that I have owned), but every Stringray and Z06 that I looked at and started (about 6 of them, plus my own z06) does it. My assumption is that it is the rush of air as the TB opens with no load on the engine.......