Vibration at idle only, not misfiring, no codes -- what to check?

[misterpepper]

'09 2.0T with 170k miles, so it could be anything. What's happening is I'm getting vibration at idle that smooths out as soon as I'm driving or anything other than idling while on the brakes. It's not as bad in neutral or park as it is in drive or reverse, almost as if the added strain on the engine has something to do with it. I wouldn't call it a stumble or misfire and no codes have been thrown. It's more like one cylinder isn't working quite as hard as the others, but only at idle. Otherwise it runs as you'd expect, nice and smooth, good acceleration with no real loss in mpg's.

I first noticed it after replacing my rear main seal. I did the swap myself and replaced the seal with the aftermarket, more conventional style seal in the bullet housing. I also drained and filled the transmission fluid while I was under there. My first thought was that I did something wrong refilling the trans but I triple checked the fluid level and fill process.

Leading up to figuring out my RMS was bad (it wasn't leaking oil, just vacuum) I had replaced the PCV, ignition coils, plugs and MAF trying to figure out why it was running poorly. About 20k miles before that my timing chain tensioner went and I had to replace the entire head, so my valves were squeaky clean. While swapping the head I noticed a small amount of carbon on the tip of one of the fuel injectors, which I cleaned off, but that might have something to do with it. Also, the PO had the stage 2 oil consumption fix done, as well as the turbo replaced.

I'm not ruling anything out, even though most of the usual suspects seem to have been addressed recently. With 35k on the clock since replacing the head it could be time for another carbon cleaning. Could my intake be failing? This would be a good time to change it, as well as maybe the injectors. I'd rather rule out what I can before dropping $400 in parts that may not fix anything. So...what's ailing my ride?

[cuda2000]

This doesnt help you much but I have the same little vibration at idle on my 2010 2.0 TFSI with 88k miles. I have owned it since brand new so I notice the idle is just a little rough. More noticeable with a/c off. Other than that it runs like a raped ape with unitronic stage 2 and a test pipe. The vibration at idle has been there a out 2 years for me. I had pistons replaced at 50k miles and timing chain tensioner replaced at 60k preventatively. In the last year I replaced the turbo, installed test pipe, unitronic stage 2, high pressure fuel pump, main fuel pump, fuel filter, all fuel injectors, had valves walnut blasted, spark plugs, replaced water pump, and replaced pcv diaphragm. Runs fantastic except for little rough idle like you said. I did most of the work myself but I had a Shop do the water pump, fuel injectors and walnut blasting all at same time. The shop never mentioned/noticed the rough idle, they just said it ran great. So I guess what I'm getting at is you may have to live with it, unless someone has another idea. I am going to replace pcv valve with newest revision just to see what happens but I'm not expecting a change. I have the part just haven't done it yet. Good luck!

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[elscotto80]

Could be the motor mounts, have you replaced those?

Any codes stored?

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[misterpepper]

No codes. Motor mounts is an interesting idea. I'm not getting any clunking like a typical failed motor mount, but since ours are fluid filled I believe it could be that they are structurally sound, just not dampening the small stuff any more.

[elscotto80]

At 170k miles and if you don't know if they've been replaced, they are the likely issue.

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[misterpepper]

Two votes for engine mounts -- sounds like I need to get some on order. Except unfortunately there are about 6 different mount part numbers that get mixed and mattched depending on transmission, drivetrain or whether the mounts contain a sensor or not. As best I can figure out, for my car ('09, 2.0T, Quattro, Automatic) I need Lemforder part numbers 3474001 and 3474301. I'm basing those numbers on this link. The cheapest I can quickly find them turns up a Porsche Macan 2.0 kit at FCPEURO for $153 shipped. Am I good to pull the trigger?

[Smac770]

Those are the two part numbers I put on my '09 2.0T quattro automatic however long ago it was.

[Der Konig]

Just have someone rev the engine while you stare at it, if there is excessive flex (which is subjective I know but should be fairly obvious) that is your issue.

Easy free test.

[misterpepper]

If they're not bad yet they probably will be before I wear this A4 out. I drove my last one to 267k and I would hope to get as much out of this A4. Reading up on it, motor mounts do seem like a likely culprit. I'll just go ahead and replace them. It may turn out to be preventative maintenance, but so be it.

[elscotto80]

I believe there are differences between auto/MT and those with and without sensors. I have mounts with the sensors, but I don't have the ADS option, so the wires just got tucked up. No biggie.

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[misterpepper]

Well it turns out that both mounts were bad. One had actually split into two pieces but neither had any fluid in them. They've been bad for a while.

I did the install myself in my garage and it took a lot longer than I had anticipated. For some reason I had it in my head that it would be about a 2 hour job but it took me at least twice that. I had some trouble getting the top motor mount bolts out because the mounts had collapsed to the point that it was hard to get a straight shot at the bolts. I pretty much followed the factory instructions rather than the 034 Motorsport ones. I'll be buying one of those engine load leveler hoists soon because working around the jack lifting the engine from underneath was kind of a pain.

The Porsche Macan kit I linked to above fit perfectly. The 2 mounts appeared identical to each other, aside from the boxes they came in. I promptly lost track of which was which so there's a 50% chance I have the mounts on the wrong sides. It doesn't seem to matter much if they are on the wrong sides. The good news is my vibrations are gone and I'm back to being buttery smooth.

[Liquid Smoke]

good to hear that did it. i have a similar thing, just relatively rough idle, nothing that bad but lately ive noticed it does get loud once im in D or R, quiets in neutral, goes up a little in Park. i have an 09 with 148k, was going to do my mounts soon too. also i believe both sides are the same thing so you're good, they fit either side i believe.

[Smac770]

I got this for doing the mounts and such work on my A4: https://www.ecstuning.com/b-schwaben.../010049sch01a/

It works well enough; the included chain is too fat to fit through the hole in the engine supports, but a high load carabiner resolves that.

It was nice to be able to get it set and the bolts removed, then be able to lift the engine up an extra inch to help slide the mounts out/in, then be able to spin it back down to the proper height for installing the bolts.

[Smac770]

The mounts appear the same L/R; the support brackets are definitely different. I don't know why Audi and Lemforder bother with different part numbers L/R, as neither include the support brackets with the mounts (except for the Audi kit that includes all four pieces).

[misterpepper]

LiquidSmoke, that sounds exactly like my symptoms. Vibration varied depending on which transmission setting you were in while you had your foot on the brake and weren't moving. Very little vibration once you were moving.

Glad to hear the mounts are interchangeable. I thought maybe the liquid used to fill them might have different viscosities per side or maybe there was a difference to the integrated sensors or something. Since they did such an abysmal job differentiating the two mounts I figured it wasn't a big deal if I got them on the wrong sides.

I placed an order for an almost identical engine support bar. Two inches shorter, but almost 1/3 the price. It'll probably take a month to get here, but I don't care.

[Theiceman]

I thought the valve inside the mount was only on one side. Not sure though. Only one side on my 14 had the electrical connector going to it..
It wasnt connected to anything either which I found odd.

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[misterpepper]

I had connectors on both mounts, both connected. Interestingly, the Lemforder mounts had the wire pigtails clipped into the mounts, leaving very little wire to work with. In order to install them correctly I had to unclip the wires (just pull out the little Christmas tree stem and remove the wire from a groove) to get enough length when reinstalling them. The little Christmas tree stem popped right into the factory holes.

[Liquid Smoke]

LiquidSmoke, that sounds exactly like my symptoms. Vibration varied depending on which transmission setting you were in while you had your foot on the brake and weren't moving. Very little vibration once you were moving.

yea ive noticed on mine i get some vibration now when accelerating, i can definitely tell it's more than the normal cabin vibration and gotta be my mounts. at first i thought maybe it was my exhaust with a leak or loose pipe or something, but i realize its the engine just making the one of the mufflers vibrate more than usual on those certain gears.

im also planning to replace the trans mount at the same time, with the Febi Bilstein part. does anyone know if it's easier to do the trans mount while doing the engine mounts? or is the labor work unrelated? i was thinking to get it done together to save on labor cost at a shop, but if it's not going to make much difference on total time/labor then i may as well do the trans mount later on and do just the engine ones for now, as i think my trans mount is fine i dont really get any clunking or excessive movement or anything when shifting.

[misterpepper]

I don't think you'll save much doing the trans mount at the same time, unless they go the route of dropping the subframe to get at the engine mounts. If you follow the factory procedure about the only labor you will save is removing the underbelly covers. I pulled the cross bracing covering the transmission to get a better place to jack the engine up from, so I would have saved that labor as well, but the factory procedure for changing the mounts is all done up by the wheel wells.

[Liquid Smoke]

gotcha thanks, i thought so but just wanted to be sure, rather not spend on the trans mount for now until it's needed, will start with just the motor mounts and see how better it gets overall.

wondering about the 2 sides, with diff part #'s, but one of them is cheaper. i wonder if you can just get 2 of that one if both sides are indeed the same? or maybe some difference in the electrical/sensor part of it?

[misterpepper]

No clue about the part numbers other than to say that they appear identical outwardly, have all the same casting marks, have the same connector and have the same part number markings. If there is any difference to the fluid inside, pressure of fill or the electrical components it can't be that important since once they are out of the box there is no way for mere mortals to tell them apart. Another indicator: 034 motorsports sells 2 different densities of aftermarket mounts and they only have one part number (per density) that is to be used on either side, regardless of whether the vehicle needs the sensor or not. You're probably safe just getting the cheapest mounts you can find that include the sensor (assuming your vehicle needs them). I'd probably stick to SKU's that are used on B8/8.5 Audi's, just in case there are differences with mounts that appear the same but are intended for other vehicle models.

[Morpheus23]

I went through this vibration at idle for some time as well (no codes). Checked vacuum and PCV, etc

Turns out both engine mounts were shot. One completely busted and the other halfway busted.

Changed them and on my way home when stopped at a red light or in traffic, I had to check the tach several times to see if the car was still running.

[Smac770]

I thought the valve inside the mount was only on one side. Not sure though. Only one side on my 14 had the electrical connector going to it..
It wasnt connected to anything either which I found odd.

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Don't you have a manual? The manuals and automatics use different mounts; the manual mounts have no adaptive feature.

[Theiceman]

Don't you have a manual? The manuals and automatics use different mounts; the manual mounts have no adaptive feature.

that would make sense.. yes i have a manual . maybe someone put a different mount in along the way and just let the wire dangle ... thats actually good news as when i put the motor back in i replaced both mounts with ones without wires... and i was wondering if i was doing something wrong.

[Ejr]

Well it turns out that both mounts were bad. One had actually split into two pieces but neither had any fluid in them. They've been bad for a while.

I did the install myself in my garage and it took a lot longer than I had anticipated. For some reason I had it in my head that it would be about a 2 hour job but it took me at least twice that. I had some trouble getting the top motor mount bolts out because the mounts had collapsed to the point that it was hard to get a straight shot at the bolts. I pretty much followed the factory instructions rather than the 034 Motorsport ones. I'll be buying one of those engine load leveler hoists soon because working around the jack lifting the engine from underneath was kind of a pain.

The Porsche Macan kit I linked to above fit perfectly. The 2 mounts appeared identical to each other, aside from the boxes they came in. I promptly lost track of which was which so there's a 50% chance I have the mounts on the wrong sides. It doesn't seem to matter much if they are on the wrong sides. The good news is my vibrations are gone and I'm back to being buttery smooth.

So you’re telling me that the vibrations at idle while in D or R with foot on the brake and they get worse when I engage the parking brake and let off the brakes - were solved! I first replaced the transmission mount, no luck - however it was an inexpensive part I got from Rock Auto. I then replaced the motor months with a Lemforder kit, the vibration was just a tad bit reduced but it kept coming back. All these replacements were done in 2021. Same brand you had bought but mine didn’t say Porsche, and if my memory serves me correctly, the mounts didn’t have connectors. I don’t have drive select modes anyway.

Pretty strange that Lemforders solved it for you but me.