I have a 2006 and have a engine knock when accelerating. Local GM dealer says 3 things. "It's normal for the engine to knock"
I installed BORLA exhaust and that is causing it and I have K&N filters in the stock air box. The Dealer said that GM tech said not to "Waste" any more time on since I "modified" the car. Come on GM, the dealer installs CORSCA exhaust and it doesn't knock does it? Anyone out there have experience with this?

 

Wow that dealer is absolutely ridiculous. Take it to a different dealer and hopefully they take better care of you. Best of luck

 

take it to a tuner--fixed

Had the same problem with my A6. Tuner fixed it and then some

 

 

Thanks guys. They also said that if I do flash it with an aftermarket tune, it will void the warrenty? We do have a good tuner around here so I might take it to him. I am also going to vist the Corvette Factory on the 23rd of this month. Do they have anyone theree that listens or is it pure GM there too?

 

You might also have a bad (too low octane) tank of gas.

 

Using either SHELL with no ethanol or BP also pure gas, no additives, highest octane on the pump.

Any bad luck with these?

 

If you didnt scan it then you dont know if it is knocking. This car has knock retard and doesnt knock. It pulls timing to prevent it. What you are hearing is unlikely to be knock so instead of guessing, take it to a tuner and get a scan. I used to hear all sorts of noises after modding with certain set-ups such as rocker arms ect....so you cant be sure what it is. I thought the same thing and there was no knock retard (of Knock) to be found.

If anyone near LI, NY wants a free scan to see if this is the case with their car, PM me and I will meet up and scan it for free. Im not selling anything.

 

Spin scanned mine and it was free..

 

I'll bet the dealer is right. I've seen that before with K&N filters.

You increased the air flow in and out of the engine with freer flowing intake and exhaust and still have the lean factory tune. That equals spark knock. The MAF is also real sensitive to the airflow across the hot wire sensor. They spend a ton of time engineering the stock filter to get the correct laminar flow through the sensor. Number of pleats, media... that all has to be fine tuned to get the flow right. Throw in an aftermarket filter and who knows if the MAF is reading correctly.

There was a huge problem with Hummer H2's spark knocking and setting codes when using aftermarket filters. A bulletin even came out advising techs to check for an aftermarket filter.

I had an 04 Z06 that I put a K&N filter in and ran into spark knock real bad at full throttle. Sounded like marbles in a can when I floored it. Put the OEM filter back in - fixed.

Knock sensors can only reduce timing. If the knock is preignition before the spark even occurs, timing changes will have no affect. It's misunderstood that knock sensors should stop all knock, not possible. They can reduce knock if low octane is the problem.

Put the OEM filter back in and see if it goes away. If it does, either leave it that way or it will have to be aftermarket tuned. A dealer has no way to alter the tune for an aftermarket intake.

 

The car isnt running lean if there isnt a check engine light. The car is running at 14.7:1 at all times (closed loop) regardless of mods. Mods would cause it to run lean but the O2 sensors read the exhaust and compensates. The only change is at wide open throttle when it would then run richer since it reads how much fuel is needed to keep it at stoic and adds the appropriate fuel to make it 14.7:1 and adds the same amount of fuel at WOT which is already to rich from the factory.

It pulls timing to prevent knock so that isnt what you are hearing unless your knock sensors arent working. Many things you hear that sound like pinging arent what you think they are.

I doubt the O2's arent working and he has a lean condition with no check engine light and the knock sensors arent working. You also pont to the fuel. If you put 87 octane in this car it wont knock. It will revert to tables that run on that fuel.

Last point; I have scanned and tuned at least 60 cars and have yet to come across even one car that is running lean from the factory. Without exception they all run in the 11.8:1 to 12.2:1 range.....very rich. At part throttle, all of them run stoic.

Your input is valued but this man needs to scan the car and stop guessing what is wrong by what his ear is telling him.

 

Are you saying that you are tuning cars to run 14.7:1 at WOT??

 

Please feel free to quote my exact words that led you to type that. In the mean time:

I specified that the cars run at 14.7 stoic at part throttle and specified that they run at 11.8:1 -12.2:1 on the stock tune. Using 2 numbers there would suggest a final tune would also have 2 numbers. But since I am not and engilsh major I added 2 words above to clarify.

I use a wideband for 13:1 in most of the band. Slightly leaner low in RPM and slightly richer at peak TQ WOT for a 12.8:1 at lowest.

The car above is running at 14.7 at part throttle by virtue of not haveing a check engine light. At WOT it is richer than stock and probably in the 11.7:1 range.

 

yeah I'm having an "off" day today.

 

Thanks SpinMonster,

For now I will keep my foot out of it. I will bite it I guess and get GM air filters. That just does not make sense to me since I have used K&N on alot of vehicles and have never had a problem and they have helped the performance. Why so different in the LS2 engine? No check engine lights, no codes from the scan tool just the noise some of the time. More in warmer weather. Does not have to be at WOT to make the noise either.

 

So if you believe the knock sensors will stop all knock, go ahead and put some 87 in and I'll bet I know what you'll hear - tons of spark knock.

Just because the check engine light is not on, does not mean the engine is running on the right A/F mixture. Just the fact that it is knocking on a hot day with a heavy foot, to me is a good indicator the A/F is not ideal.

Been there, done that with K&Ns. Put one in, knock knock knock. Take it out, back to normal. Its the airflow over the MAF is messed up, gives the ECM a false reading of less air than is actually coming. Less air (the ECM thinks) means less fuel, equals spark knock. Take all the timing out you want, it's still going to knock if it's preignition. Timing has no affect on preignition. That's from too hot, too lean, self igniting under pressure.

I've taken two vettes side by side with scanners. Both were 04 Z06's when I was trying to figure out why mine was knocking with a K&N. With the K&N the Grams per second air flow was different at idle, the 02 crosscounts were different also. The filter was definately making it run different. As soon as I put the stock filter back in, the spark knock stopped. It never once set a code, just a lot of heavy throttle spark knock. Since then I have talked to a powertrain engineer that works with induction systems. He said they go through extensive testing to get the airflow right across the MAF, media type, number of pleats in the media... Change something there, and who knows if the MAF will be reading correctly.

You can prove it to yourself by taking out the K&N and enjoying knock free full throttle runs.

 

There are many, many other Corvettes out there with higher flowing intakes like Vararam, Honker, Blackwing, etc that flow MUCH more air than simple K&N filters in the stock box; most couple them with higher flowing exhausts as well, and they dont knock. Ive even seen guys remove their MAF screens, which really changes flow, and they dont knock either...sounds like it may be something else.

You need piece of mind, so get a scan and know whats going on for sure. If it's truly knocking, it will show up and can be corrected. Better yet, get a tune and optimize your engine for the mods you want to run.

 

Yes it is strange that many systems don't knock and some do. But I've done exactly what he's talking about - put a K&N filter in a stock intake housing and gotten tons of heavy throttle spark knock. Maybe some of the complete systems are better engineered to get the flow right across the MAF. Easy way to prove it. Put the stock filter back in and see if the knocking goes away, mine did.