FIXED: "Flutter" sound only under boost. Ideas? - 2006 Grand Prix GT

**Scottydoggs** · 10-06-2015

i do what i want lol i figured it was best to not pull the T off under the snout, cause it would break and id have to fix it. so i pulled the booster line off pinched it so the car dont stall, then poured it in the booster, well it sucks it in pretty much, dump the last little bit of the 1/3 of the can in and let it stall or shut it off quick. then let it sit for 20 to 30 minutes.

**nickbuol** · 10-07-2015

When I did this a year ago, I followed one of those line from the T under the snout, and it goes over to the solenoid that I mentioned that I replaced. Here is a picture that I took when I did this a year ago. If you follow the line (from the T) in the front, it comes right up behind the oil filler area and is super easy to access. I am planning on doing the same again, I guess.

**nickbuol** · 10-07-2015

OK. So i just finished Seafoaming, searching for leaks, and then driving until the Seafoam was no longer smoking the car, plus a couple of extra miles.

It gave me an opportunity to check the whole exhaust system, and I learned a couple of things. 1) my downpipe isn't leaking where they welded it like I thought, so the exhaust noise is coming from elsewhere, 2) I think that the "elsewhere" is from the passenger side muffler as there was a small hole towards the bottom on the "front" of the muffler that has smoke coming out of it.

What I didn't figure out was what was causing the noise still. I did, however, see some smoke from every place that the exhaust connected to the next part of the exhaust. Between the front manifold and the crossover pipe, between the crossover pipe and the rear manifold, and between the rear manifold and the downpipe. This was somewhat evident when I was just putting the seafoam in as I was getting smoke under the hood while putting it in slowly. At idle, you could see smoke seeping out of those gasket areas, and of course more when throttle was applied.

Not sure how "sealed" that part of the exhaust should be, but I didn't notice any smoke where the downpipe connected with the resonator (although the resonator was replaced about 2 years ago, so it would have had a new gasket.

Nothing else seemed out of whack...

**Scottydoggs** · 10-07-2015

sounds like your exhaust is leaking all over the place. good time for headers?

if the hole in th emuffler was a 1/8 inch round hole in the bottom, its normal, thats to drain condensation. unless its a rusted out hole.

**nickbuol** · 10-08-2015

Ha. Headers... I should have done that when I had my 2000 GTP instead of the upgraded downpipe and PLOG back then.

I don't plan to really mod the car, and headers will be a bit spendy, even the cheap ones.

Might have to call an exhaust shop and get their take on it. I mean, it shouldn't be leaking at those spots, but maybe they can just do it instead of me messing around with it and then see if they find any other problems.

I still don't think that these leaky areas are what is causing the problem though.

**Scottydoggs** · 10-08-2015

if you saw smoke come from the the two flanges they are leaking for sure.

like i said in the first vids, it does have that sorta exhaust leak sound.

**nickbuol** · 10-12-2015

So I ordered a new catalytic converter last Thursday night, and it showed up today. I was spraying all of bolts with PB Blaster for a few days which really helped to get things apart yesterday waiting for the part to show up today. I picked up new gaskets yesterday, and when I couldn't get the o2 sensor off of the original (no matter what I did), I had to buy a new sensor too. Sucks to spend the extra $65, but at least it was on sale (Got the Denso one vs. the Bosch since people have much better luck with Denso). Picked up a few new bolts, washers, and nuts for where it connects to the resonator, and new "exhaust studs and bolts" for up front.

Everything came apart easily, like I said, minus the o2 sensor.

The new Magnaflow downpipe/cat showed up at 2:00pm today, Everything looked good, and it even came with gaskets. The rear gasket looked great, so I will return the one that I picked up, but the front gasket from Magnaflow was a "ring" style. I tried for about 10 seconds to install that one before I gave up and said "that is stupid." There is no way to hold that "ring" style gasket in place while putting things togethers, so I used the one that I picked up myself as it was the same style as the factory/oem one with the "bolt holes" to hold it in place while putting things together. 45 minutes later and everything was together, I took a test drive, and cleaned up the tools and swept out the garage...

Oh, and the problem (noise) is fixed!

So this was a long time coming as the flex-pipe part of the downpipe/catalytic converter has been cracked for a long time and it just hit a critical point.

At some point I will replace the gaskets on both ends of the crossover, but for now the major problem is resolved. It is so nice not having any noticeable exhaust leak noise (there has been a "tinny" sound for a long time, just not loud like what I had in the videos).

What is so frustrating is that I told multiple people both online and in person (I.E. the repair shop that wanted me to replace supercharger parts), that it sounded like an exhaust leak. The repair shop, who knew that the downpipe was leaking, still never thought that it was something else. Seems like the only ones thinking that it was exhaust besides me (I didn't mention it until 6 days ago and several posts into this topic though) was you Scotty...

Speaking of Scottydoggs, thank you so much for sticking with me through all of this. Sometimes it just takes an extra perspective on the situation to say, "keep looking at the basics. If there is a known exhaust problem and it sounds like an exhaust problem, fix the exhaust problem first before worrying about more unusual items like the supercharger." OK, that is more of a combination of all of the ideas here and my own, but you get the point.

Thanks also to J57ltr and 99GT2dr for some ideas along the way as well.