Cold weather vibration

[Nillious]

My car has a bad vibration under 2k RPM only in cold weather. You can feel it in the floor and center console and steering wheel. Its under 2k but worst from 16 to 1800 under load and actually worse on deceleration in that rpm range. Funny thing is it's completely smooth if it's above 50f. Gets progressively worse the colder it is outside.

Even when it's cold if I let the car sit and idle to warm up under the car and hood it will be smooth even in cold weather. After I drive some distance in cold weather it come back as everything cools back down. After I get gas and it's sat for a few minutes it's smooth until it cools again while driving. It never happens if it's warm weather even when the engine is still cool. I have done motor mounts and it didn't change anything.

To be clear this is an engine vibration not a rotational. Does it even in neutral when cold weather is present. Any ideas would be much appreciated.

[carguy19]

Until I read the last sentence, I would have suggested checking the tires. Sometimes when the car sits overnight on Z rated tires and its really cold out, they get some flat spots on them until the tires warm up. This happened to me and drove me crazy until I figured it out.

Does it do it when you're driving if you put the car into neutral and let it roll in neutral?

I would also do some steering maneuvers to load each corner of the car and rule out wheel bearings.

[Nillious]

It is entirely rpm based. Any gear any speed and in neutral sitting still.

It does it with engine fully warmed even after driving for over an hour. Any rpm under 2k I can feel but definitely worst between 16-1800. I even feel it at idle.

Again it completely is fine when ambient temps are up above 50. My tires do flat spot overnight but that is a speed based rotational vibration. This is entirely rpm based and only when the under carriage is cold. Even if it's ten degrees outside and I sit and idle for several minutes allowing it to warm up the area around the under carriage the vibration is gone. Then I drive a few miles and it cools down then it's back until either idle or park with a hot engine or ambient temps are over 50.

I start to feel it at 45 ambient temps but it's minor. At 30 degrees or below it gets really bad. It is something transferring vibration from the engine to chassis but only at cool temps.

[carguy19]

It is entirely rpm based. Any gear any speed and in neutral sitting still.

It does it with engine fully warmed even after driving for over an hour. Any rpm under 2k I can feel but definitely worst between 16-1800. I even feel it at idle.

Again it completely is fine when ambient temps are up above 50. My tires do flat spot overnight but that is a speed based rotational vibration. This is entirely rpm based and only when the under carriage is cold. Even if it's ten degrees outside and I sit and idle for several minutes allowing it to warm up the area around the under carriage the vibration is gone. Then I drive a few miles and it cools down then it's back until either idle or park with a hot engine or ambient temps are over 50.

I start to feel it at 45 ambient temps but it's minor. At 30 degrees or below it gets really bad. It is something transferring vibration from the engine to chassis but only at cool temps.

Check your crank pulley and make sure its not starting to come apart inside (the rubber part). They go bad all the time.

[jbain2]

Nvm. Just saw you did motor mounts.

Do you have any sort of inserts and have you done trans mount?

Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)

[A4Qwattro]

Have you ever had carbon cleaning done?

[A4Qwattro]

I would do a thorough inspection of the exhaust system as I bet that's where it comes from. The exhaust system expands a lot between cold and hot so it's possible that when the exhaust is cold and shrunken, it's causing a vibration that goes away when it's hot. Usually it's related to how things sit inside the mounts. IIRC, these motors are very particular between 1000-2000 RPM and there can be an exhaust rattle/vibration in that range if something is no longer sitting the way it was from the factory. Clamps can loosen.


Is this the noise: https://www.youtube.com/watch?v=JkwZwjGxdMM&t=21s

Check your downpipes. It was suggested that loosening and adjusting the fitment of the exhaust helped. Also check the flexpipes.

[Htown213]

Funny things is I experienced that last year. Thought it was the motor mounts. It's been colder this year but haven't noticed nearly as much vibration in that rpm range. Sorry, nothing to add to this thread except it might just go away on its own.

[Nillious]

I would do a thorough inspection of the exhaust system as I bet that's where it comes from. The exhaust system expands a lot between cold and hot so it's possible that when the exhaust is cold and shrunken, it's causing a vibration that goes away when it's hot. Usually it's related to how things sit inside the mounts. IIRC, these motors are very particular between 1000-2000 RPM and there can be an exhaust rattle/vibration in that range if something is no longer sitting the way it was from the factory. Clamps can loosen.


Is this the noise: https://www.youtube.com/watch?v=JkwZwjGxdMM&t=21s

Check your downpipes. It was suggested that loosening and adjusting the fitment of the exhaust helped. Also check the flexpipes.

You may be on to something. I had this exact rattle about two years ago. The noise was the internals of the resonator in the left down pipe. Not my video but exact noise. https://m.youtube.com/watch?v=ujeTIi5gs8k

It was vibrating and was loose internally. I didn't want to cut the stock down pipes cause he didn't have any stainless pipe at the shop and I'm in pa. His fix was he took a piece of round stock for making hangers and tied the two down pipes together with a cross brace. This stopped the down pipes from being able to vibrate and move.

That was early spring so it was warm out and everything was fine but when cold weather came back that was the first I noticed it. I wonder if for some reason all that movement of the down pipes being stopped it's transferring into the cabin somehow. The only in cold weather part is what's confusing.

[carguy19]

You may be on to something. I had this exact rattle about two years ago. The noise was the internals of the resonator in the left down pipe. Not my video but exact noise. https://m.youtube.com/watch?v=ujeTIi5gs8k

It was vibrating and was loose internally. I didn't want to cut the stock down pipes cause he didn't have any stainless pipe at the shop and I'm in pa. His fix was he took a piece of round stock for making hangers and tied the two down pipes together with a cross brace. This stopped the down pipes from being able to vibrate and move.

That was early spring so it was warm out and everything was fine but when cold weather came back that was the first I noticed it. I wonder if for some reason all that movement of the down pipes being stopped it's transferring into the cabin somehow. The only in cold weather part is what's confusing.

Either that or the weld cracked or broke from all the movement and heat cycling, and it's doing the same thing again.

It sounds like it might be expansion/cold related. Maybe once it's hot it expands enough not to make noise? Also do you have cats on your car? Are they stock/still have the internals? The cat pipe brackets and tubing are known to break or crack over time because of the extreme hot and cold. With all the discussion on this thread, I would bet that it's something exhaust related because its present in the cold and improves with heat (expansion).

Just another guess.

[A4Qwattro]

You may be on to something. I had this exact rattle about two years ago. The noise was the internals of the resonator in the left down pipe. Not my video but exact noise. https://m.youtube.com/watch?v=ujeTIi5gs8k

It was vibrating and was loose internally. I didn't want to cut the stock down pipes cause he didn't have any stainless pipe at the shop and I'm in pa. His fix was he took a piece of round stock for making hangers and tied the two down pipes together with a cross brace. This stopped the down pipes from being able to vibrate and move.

That was early spring so it was warm out and everything was fine but when cold weather came back that was the first I noticed it. I wonder if for some reason all that movement of the down pipes being stopped it's transferring into the cabin somehow. The only in cold weather part is what's confusing.

Exhaust systems expands a ton when hot. It also shrinks when it’s cold. That’s why it’s on hangers and flex pipes. So that explains why it’s only an issue when it gets really cold. The amount of expansion and shrinkage is precise and exact as a function of temperature because that’s just the law of materials like steel. At a given temperature a steel will expand to a known ratio.