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My supercharged 2005 Grand Prix which just turned over 90k miles is exhibiting a problem which I’ve never experienced or even heard of it happening. The car has a pair of Borla ProXS oval mufflers installed, and has had them for over ten thousand miles. The cat and resonator are untouched. It’s not obscenely loud, but there’s a clearly audible deep tone inside the car accompanied by a fit of crackling and popping whenever you let off the accelerator. Or rather, there USED to be. The car was in a local body shop’s possession for two days having hail damage repaired. When I got it back, I immediately noticed that I couldn’t hear the engine over the radio anymore. I turned the radio off and sure enough, this car is quieter than it was with it’s factory mufflers. It still has the deep tone to it, but its so extremely inaudible that now I have to watch the tach so I know when to shift, which is something I have NEVER done in this car, even when it was stock. My dad’s 2013 2.5L Altima has a louder engine. To cover all of the bases I asked people at work, who hear me tear out of the parking lot at WOT most days if the car sounded quieter to them and everyone agreed it did. Now, you only hear engine bay noise such as the fans and injectors and valves, until about 3000 rpm when the supercharger whine drowns all of that out. The only time you hear any exhaust noise is if I’m doing about 75 and I drop the transmission into 2nd gear, running the RPMs up to about 5700 or so without touching the gas pedal. At this point, it sounds like it used to. The drone fills the cabin and it crackles like a rally car. As soon as you apply any throttle, though, it goes silent again.
So basically, my aftermarket mufflers stopped being noisy. There’s no way they took ten thousand miles to fully break in. My complete shot-in-the-dark guess is that my catalytic converter or resonator have internally self destructed and are plugging up the exhaust. However, I have no loss of power or fuel economy or CELs. Thoughts?
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Well I can go cutting the exhaust apart, but I can’t drive across town to the muffler shop to have it welded back together, then. The text in your signature applies here, lol
[quote=”LJ11194″ post=110954]Well I can go cutting the exhaust apart, but I can’t drive across town to the muffler shop to have it welded back together, then. The text in your signature applies here, lol[/quote]
Ahhh.I didn’t realize everything was welded. good point. 🙂 The only thing
you can do is a vacuum gauge to see how big of a restriction if any. I doubt
its the resonator. Thats usually just a large chamber pipe to cancel sound.Sounds like the bodyshop corrected the install. Did you ask them what they did? get on the phone with the tech?
Quieter is better, no?
“a fit of crackling and popping whenever you let off the accelerator. “
Is it possible you got used to the noise and therefor thought it was normal? crackling and popping doesnt sound like something I want my car to sound like…
As a matter of fact, no, quieter isn’t better. Not for this car and not for me. I first thought I had just gotten used to it which is why I asked others who hear the car every day and they agree with me. The body shop only did PDR on the hood, trunk, and roof. They didn’t touch the exhaust especially since there was nothing to correct. Later when I’m not at work I’ll see if I can pull up the video I made of how this car sounded before (also in the video is a stock 350Z to compare) and make one of the difference now.
That certainly is strange. If the body shop didn’t mess with them or change anything, I would say that something may have come apart internally inside the mufflers. If this happened, that might explain why things are quieter. You don’t have to remove them or cut them open, just bump them with a rubber mallet to see if you hear anything rattling inside. If you hear something this might support this theory.
Keep us posted.
I tapped on the mufflers and they are fine. Just a hollow thud when I hit them. Here is the video of how the car sounded before: https://www.facebook.com/video.php?v=741441325877693&set=vb.100000354961213&type=3
I believe he has this shared publicly so you should be able to view it. If not, I’ll rip it down and put it on youtube. I tried making one of how the car sounds now but my phone’s microphone barely picked anything up. If you know what a bone stock 3800 sounds like though, you’ve basically got it. It really sounds like the stock mufflers were put back on, and some people I know thought that’s what I had done.
This weekend I intend to get the car on some jack stands and give the catalytic converter a couple taps as well.
EDIT: Car just started to idle a little rough. Not sure if/how this is related. It also runs a little rough at lower RPMs when cruising. I would like to try the exhaust restriction test with the vacuum gauge, but is there anything special that I need to do because the engine is boosted?
It occurred to me that immediately before dropping my car off at the body shop, I had filled the gas tank. I filled the tank again yesterday and this morning, a few dozen miles into the new gasoline, the car sounded normal again. It also has ceased to run rough. I believe that I got some low octane or bad fuel. Is it possible that the PCM pulled enough timing away that it actually ran more quietly?
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