Hello all, I recently purchased a 2009 Coupe with 25,000 miles. This is my very first corvette so I am still becoming familiarized with them. I am having a very odd issue that is difficult to explain so please bare with me and any advice or tips would be appreciated. First off, like I said before it is a 2009 Coupe w/ 25,000 miles and an auto transmission. The only performance modification the car has is Corsa Catback exhaust. I am the second owner, and the car is very clean and was well taken care of from what I can tell. Now the issue I have noticed is that after I have floored the car for a few moments and let back off, the car makes this weird noise and vibration. It almost sounds like the exhaust is plugged or restricted, even though that is obviously not the issue. I don't know if the car is running rich, if I have a fuel injection issue, an ECU issue, I am just clueless. Keep in mind that the car ONLY does this after heavy throttle and ONLY after I have backed off the throttle. It usually makes the noise right at 1,500 RPM and goes away within a minute or two. I also seem to have a loss of power when it is doing this. I am just clueless as to what might be causing this. I have a full warranty on this car so Im not too worried about it. I would just like to figure out what it could be so I can have it fixed. All suggestions are appreciated. P.S This is my very first post on the forum!

 

Congrats and welcome! Sounds like a loose exhaust check all connections.

 

It may be when you let off the gas, it deactivate to gas saving mode. When I got mine I also wondered why it seemed rough when letting off the gas. Maybe the problem?

 

Any codes set?
Be good knowing if something's setting a code.

In the absence of a code it 'sounds' mechanical from your description. Only happening under decal, then fading. Maybe torque tube bearing(s) beginning to go bad? Bad motor mount?

IF you can reliably get this to happen a dealer tech has someplace to start troubleshooting this would be the good news. And even better news is you're covered under warranty.

 

I will check into that. Thanks.

 

No I don't have any error codes at the moment. It doesn't happen under deceleration, but once I have already slowed down to a cruising speed and hold that certain speed. If I begin to accelerate again, even a slow acceleration, the noise goes away. Someone else mentioned a loose exhaust which makes sense but it only does it under certain conditions which leads be to believe it is something else. My girlfriend had a loose exhaust issue on her mustang and her car made a god awful noise at the same RPM in every gear no matter the circumstances. I could duplicate this at a dealership pretty easily as long as the mechanic isn't scared of high speeds. When I bought the car 3 weeks ago, I bought a 60,000 mile bumper to bumper warranty that will cover me until the car has 85,000 miles.

 

Corsa recommends re-torquing the clamps (49 ft/lbs) after the car has gone through a couple heat/cool down cycles after installation.

This step is often overlooked with DIY installs.

Hope this is your issue and not the torque tube related problem Landru mentioned.

Good Luck and welcome to the Forum.

 

The least expensive "fix" is the above to do, re-torqueing the exhaust. W/o any codes set, it's hard to diagnose what else could be wrong, short of doing a ride-along, or placing a "noise meter" on the car. Altho seemingly too early, let's hope it's not the torque tube.

Odd as this might seem, I'd go thru the engine and make sure all spark plug wires are clicked on each plug. There are many potential things that it could be, but let's start out with the least expensive.

BTW, do you have any indication that the car was ever otherwise altered for racing such as headers?

 

There is a good possibility that was never done. When I purchased the vehicle from the dealership, I could tell that the exhaust was nearly brand new if not completely new. The inside of the exhaust tips were completely clean with no black to speak of. Also the exhaust seemed almost abnormally quiet for a Corsa Exhaust. Once I put about 500 miles on the car, the exhaust seemed to almost double in overall volume.

 

If the issue was torque tube related, what are some things I need to look for in the future? Right now, I am thinking that the exhaust needs to be adjusted. But for future reference, what do I need to be on the lookout for that would be a sign of a bad torque tube?

 

UPDATE: I took my car in to have the exhaust re-torqued and it did not fix the problem or even improve the problem. Not exactly what I should look into next. I took the car and had it put on a dyne and the issue could not be duplicated for whatever reasons. Power levels and air/fuel ratio looked normal. My car was running a little rich but the mechanic said this was normal for stock cars. Any recommendations on what my next step should be?

 

Well, this is a long shot and probably a worst case scenario, but...

Could it be the lock-up clutch plate on your torque converter is not letting loose after it engages? After you get to cruising speed and the engine settles down, the lock-up plate will engage to make the impeller and the turbine spin at the exact same rate. Under load, the plate will release to provide more torque to the transmission/wheels. The material on the plate is a friction material just like a manual clutch or a brake pad. If that material layer is damaged or somehow coming loose inside the converter, I could see it causing a rumble noise and loss of power under the conditions you have described.

 

What ache said above is a long shot, but no more than the torque tube. I'm by no means an expert on torque tubes. But, a little advanced searching using the "search" in the red band above, then going to "advanced search" and using just "torque tube" as key words on the upper left (and limiting it to C6 Gen and Tech), brought forth these threads:

https://www.corvetteforum.com/forums...rchid=45649793

I'd suggest looking at them and reading the relevant ones. See if any of the issues are similar. I've read of a few problems w. tt's but not very many over the years. Keep us posted on what you're doing; it may help someone else down the road. And good luck!

 

Thanks for all the info. I might just take it up to my local dealership and duplicate the issue for the main mechanic and see what he has to say. Like I said before, the car is under a complete warranty so GM will have to cover the costs thankfully. I can't take it up there anytime soon due to weather but I will post an update as soon as I figure everything out. Thanks again to everyone who responded. The help was much appreciated.