VIbration at 2200-2400 RPM on deceleration

[PSUGOLD]

Just wondering if anyone has had this issue, and if so, what it was. I did a forum search, found a few topics, but nothing really was resolved. Basically, when I decelerate, I can feel a slight vibration and the exhaust gets a bit louder around 2200-2300 RPM. I can always tell when 2200 hits as this always seems to occur now. I've noticed it over the past couple of weeks. I am taking the car to my local guy next week for rotors/pad installation and to check the exhaust for any leaks, so I wanted to bring this up too and see what he thinks.

ANy ideas from guys/gals here?

Thanks.

[jimrobbington]

I'd be willing to guess it's just the exhaust rubbing against the frame/subframe somewhere that is only noticeable at specific resonance. Probably just need a quick adjustment somewhere

[quickglx]

Hold it around the RPM where you feel it most, watch the downpipe flex joints. My guess

[PSUGOLD]

Thanks, going to check that out when they have it on the lift. Borla had mentioned the flex joints can have issues in northern states where the roads get salted. I will have the shop adjust them and check if they notice any sign of a slight leak too.

[MrFunk]

I'm going to bet it's your downpipes. During the winter when it's really cold I get a vibration between 2100 and 2200 rpm. Got the car up on the lift and confirmed it was the downpipes vibrating. Seems the harmonics of the motor and the aftermarket exhaust just got them vibrating right at that RPM. Let us know what you find out though...

[PSUGOLD]

I'm going to bet it's your downpipes. During the winter when it's really cold I get a vibration between 2100 and 2200 rpm. Got the car up on the lift and confirmed it was the downpipes vibrating. Seems the harmonics of the motor and the aftermarket exhaust just got them vibrating right at that RPM. Let us know what you find out though...

What was the fix? Just a simple adjustment/tighten? The Borla is Cat-Back so maybe it has to be adjusted where the front pipe connects.

[PSUGOLD]

Well, little update. I took my car in to get brakes/tires installed, and we had it up on the lift. I got it to 2200 RPM, saw and felt the vibration. Mechanic said both sides of the exhaust was shaking and the engine was vibrating too. Did not look like any issue with the exhaust, but possible engine mount issue. It only vibrates at the 2200-2400 RPM level too, smooth higher and lower. May have to take the car in and have Audi look at it, also the nasty noise from the underside when I turn hard left which may be the Sport Diff or quattro.

[MrFunk]

It may be engine mounts if you're having vibration when you turn also. Very easy to identify faulty engine mounts.

BTW - there was no fix for mine - it only acts up in the winter when it's very cold out.

[jsh139]

Well, little update. I took my car in to get brakes/tires installed, and we had it up on the lift. I got it to 2200 RPM, saw and felt the vibration. Mechanic said both sides of the exhaust was shaking and the engine was vibrating too. Did not look like any issue with the exhaust, but possible engine mount issue. It only vibrates at the 2200-2400 RPM level too, smooth higher and lower. May have to take the car in and have Audi look at it, also the nasty noise from the underside when I turn hard left which may be the Sport Diff or quattro.

Take it to AWE and have them flash back to stock first.

[kirbs69]

Might be a silly question, but have you replaced your transmission mounts with any of the poly ones? Or the 034 billet insert for example? vibration on mine is noticeable right at the 2250-2750 range as a result of these.

[SteveYem]

If I remember correctly, I had this issue on my 2015 S4 when I had the stock downpipes installed. In fact I may still have had the complete stock exhaust installed at that point. I would feel it when coasting down in gear as well as when the revs dropped after blipping the throttle. I had forgotten all about it until reading your thread. I have since installed aftermarket downpipes and no longer feel the momentary vibration.

[PSUGOLD]

Might be a silly question, but have you replaced your transmission mounts with any of the poly ones? Or the 034 billet insert for example? vibration on mine is noticeable right at the 2250-2750 range as a result of these.

Nope, no change there.

SteveYem, downpipes are stock too, but I have had the aftermarket cat back for well over a year now too, this just started a few weeks back. I can give that a look though for sure. We had the car up yesterday and at the 2200 RPM mark the whole engine started to vibrate some, said didn't look like an issue with the pipes, but he could have been wrong.

[PSUGOLD]

Update. FIXED. I had an exhaust leak at the flex joint of the front pipes. Borla sent me new pipes, had them installed yesterday, vibration gone. Had a feeling this may have been the culprit, and now it is smooth all through the RPM range. Nice. Also, the nasty noise I had posted about while turning left may be gone too. I sorta hear something and feel a little bit, but not like it was before.