I have an 08 4.0 Mustang and had the FRPP dual exhaust installed recently. I don't know if there is any relevance in this being the cause but when idling in drive (I have an automatic), it idles louder than it had before, mostly when the A/C is on, causing a shudder/vibration. I know its supposed to be different its just a lot louder than before. When I shift into neutral, it becomes quieter (like it should be), and the noise/shudder/vibration decreases substantially (again, like I'm thinking it should be). When I shift back into Drive, it'll get louder again. Also, if I gently tap the gas to get the rpms to around 750 it will decrease. PLEASE help, its really just an annoyance.
I didn't know that the computer had to learn mufflers the vibration is normal from what i have seen and heard i have been around plenty of Mustangs my whole life and when going from single exhaust to dual the backpressure is alot more free and thus you get shuddering from the lope of the engine at least this is what ive been told cause ive asked the same question myself
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2007 shelby its actually a V6 i call her Shelby so far i have a screamin demon coil and live wires and a roush CAI and SCT SF3 tuner.
I'm having the same issue. I'll try the battery trick but my shudder didn't show up until about three months after the installation.
Sounds like a heat shield or something like that. It's going to a very thorough mechanic on Wednesday to be checked.
I'm having the same issue. I'll try the battery trick but my shudder didn't show up until about three months after the installation.
Sounds like a heat shield or something like that. It's going to a very thorough mechanic on Wednesday to be checked.
My mechanic didn't try the battery disconnect but did notice that the aftermarket plenum cover I installed was touching the underhood insulation and, after removal, showed a couple of areas that were rubbing on the passengers side of the intake.
We removed the cover and have not heard the vibration since. I'll wait a couple of days before I pass judgement, though. I might try the battery disconnect this weekend.
Meanwhile, I'm taking some measurements to add some insulation or do some material removal on the cover to prevent the rubbing. I'd really like to leave the cover installed as it prevents a lot of road trash from settling in the intake manifold area.
For everyone's info, I installed a K&N cold air induction system about a week before the exhaust system was installed and added the plenum cover at the same time. I noticed no vibrations at all untill about three months after the exhaust system was installed.
I'll keep the forum posted as to my progress. I'd like to hear from anyone else who has had vibration issues as well.
Well, picked it up Wed nite and the mechanic found nothing at all loose anywhere on the chassis, exhaust system, trunk, interior...nothing.
He did notice that the underhood insulation had sagged a little and was starting to rub on the aftermarket plenum cover I have installed, so he removed it. By then it was warm so he figured we could try it out in the morning.
It was nice an quiet yesterday morning.
Last night? The noise is still there
This weekend, I'll try the battery disconnect and I'll also remove the underhood insulation.
I want you to try this, cuz I had the exact same problem. Have a helper with you, put some wheel chocks under the rear tires, put the e-brake on (hard) and put it in drive, and run the rpms up a bit to load the drivetrain. Not enuf to move the car, but enuf to preload the transmission, driveshaft and rear end. While the car is under load as such, check all clearances, espcially the hangars on the aft of the mufflers, When the car is under load, the distance from the hangar post and the bumper decreases considerably due to the fact that it (the exhaust pype) is attached to the engine, wich moves under load. Mine looked fine up on the rack, had like two inches clearance, then when under load, the gap closed, and the hangar was banging against the rear bumper sheet metal. That may not be your exact problem, but you might find it when the drivetrain is sprung as I said. BE CAREFULL, and pick your helper wisely, so they dont kill you
I did have that hanger checked, but then it was SUPER loud. I had it checked, and the trimmed about an inch and a half off of the driver's side muffler. Now it just seems RPM-related. Again, when its in Drive, and the A/C is on while idling, the car shudders almost like it's about to stall, but when I shift into neutral, the RPMs go up a notch and it seems to be gone. Only happens during idle. I am thinking I need to have it so it idles in Drive at the same RPM position?
I think I found the source of my noise.
This Past Saturday, I disconnected the battery for 30 minutes. While it was disconnected, I started feeling around for ANYTHING that might be able to vibrate. Well, I found the two aluminum heat shields above the Cat converters and when I tapped one of them, BINGO...the shudder I'd been hearing. Some graved had gotten wedged between the body and the shields and they were making a nasty noise. I got all of the sand and gravel out from behind the shields and have not heard the noise since. I think I'll put a couple of hi-temp silicone rubber gaskets behind the shields during the next few days.
After re-connecting the battery, I did notice that the idle was a little smoother, too. I'll most likely install a new set of spark plugs and some better wires, too.
Im in college so I dont really have any tools but will be disconnecting the batter once I get my hands on some to disconnect the battery.... hope it works! Also having a shop look at it on Tuesday.
I just got back from the shop and he tightened the clamps on the FRPP exhaust, and now its a little less audible, but you can still feel it. He said that the stock exhaust system came with vibration dampers installed at one or two spots, and these may need to be installed on this system. V8's do not have them stock, due to the vibration issues that only pertain to V6's. So, does anybody know where I can get a couple of these? A picture can be found at this link: 2005 Ford Mustang Vibration Damper Photo
2008 Mustang V6-Vibration/Shudder at idle HELP 
the vibration is normal from what i have seen and heard i have been around plenty of Mustangs my whole life and when going from single exhaust to dual the backpressure is alot more free and thus you get shuddering from the lope of the engine at least this is what ive been told cause ive asked the same question myself
