Need some desperate help with vibrations when accelerating

[longman h]

Check your wheel nuts are tight.

Done and all is fine.
Tyres pressures are also OK.

Something I noticed today is that it seems to become more prominent once the oil temperature has risen. So when cold or sat for a while, it starts off OK.

Its doing my head in now and the frustrating thing is, we'll be driving about 250 miles this weekend.... Brilliant!!

[longman h]

If it's not coming from the engine (you need to definitively eliminate that possibility) then it could be coming from the inner drive CV joint. In this case, I bet they pulled it off to do the G28 and have damaged / worsened it.

I still need to check this Shop.

[Shoppinit]

Check your wheel nuts are tight.

Something I noticed today is that it seems to become more prominent once the oil temperature has risen. So when cold or sat for a while, it starts off OK.

Sounds like a misfire.

Can you check your mixture?

[longman h]

Err..... Without sounding like a melon, how do I do that?

[longman h]

Also, a misfire should create codes shouldn't it?

[Shoppinit]

You'd think. Odd that you haven't if it is misfiring. But there are quite a lot of conditions where the engine doesn't / can't check for misfires. Or maybe it's not misfiring but missing.

Did they have the plugs out? Coil packs off? Might be worth unplugging and replugging the coil packs and checking the connections.

For the mixture, you can check group 32 to see what your trim values are.

[longman h]

Update: Didn't have a chance to get VCDS out today to see what the mixture is but I am now pretty sure the vibrations relate to vehicle speed and not the engine.

I'll try and have a look at the fuel mix ASAP though.

[sweegie]

If it's speed and torque load sensitive, I'd say it's another vote for a CV joint from me.

[longman h]

If it's speed and torque load sensitive, I'd say it's another vote for a CV joint from me.

That's what I keep thinking but when they had it up on the ramp, they reckon the CV's are ok. Is the inner CV easily accessible/visible?

[Shoppinit]

Sure. For an RS6.

[longman h]

So we managed to complete our 200 odd mile round trip down to Dorset trouble free which was a relief but it gave me an opportunity to study the vibration a little more, so here's the analysis;

Accelerating gently up through the gears to around 60/70 is where the vibrations seem to be worse but when I get closer to 80 and start just cruising, the vibrations seem to come and go in a vibrating pattern. It's as if the vibration starts, then slowly gets less and less then starts to build again. This is all at a constant speed.
Even when I reach higher speeds this seems to happen.

Now the really strange thing is, on the way back home today when we were around 10 miles away from home, the vibrations had pretty much disappeared.

Does anyone have any ideas?

I'll be driving locally tomorrow so will report back with my findings again.

[ahoooga]

All wheel nuts tight ?
Tyre pressures correct ? 40-42 ish psi ?
All wheels still correctly balanced ?
All rims run true or are they warped/damaged ? a wheel balancing machine is the easiest way to check this.

Tyres in good condition with no lumps of tread missing and not warped ?
Tyres matched up all round ?
Front tyres a match for 'El Knobbo' ?

curiosity , what tyres/sizes and pressures are you running ?

all the above are the easiest cheapest things to check and sort out , if none of them help, then you can start working back though the drive train ..............and your wallet

The fact you mention that 10 miles away from home the vibrations had pretty much disappeared ,makes me think an oval'd/deformed tyre or rim as the culprit. the fact you've done a few miles since this started suggests the affected tyre/wheel has now worn down so it runs true , check for excessive wear on all 4 tyres. It also suggests under inflated front tyres, and 'el knobbo' has done its work , but you have been lucky and it hasn't gone through the carcass completely.

any play in any suspension arms and DRC ?
you also mentioned you was after a steering rack for a plus, this isn't related to the current problem is it ?

[adsgreen]

Misfire codes are not always a dead cert (the criteria for testing and logging in the ecu are a bit 'varied')
So to confirm - it happens under load at speed but as soon as you release the throttle the vibration goes?
Doesn't matter what gear - the speed is the same?
I would have said wheel weight too but that doesn't vary depending on throttle.
Driveshafts a possibility but other possibility are engine mounts (but as they are active tend to throw a code)

[longman h]

Misfire codes are not always a dead cert (the criteria for testing and logging in the ecu are a bit 'varied')
So to confirm - it happens under load at speed but as soon as you release the throttle the vibration goes?

Yup

Doesn't matter what gear - the speed is the same?

The vibrations get more pronounced when more throttle's applied

I would have said wheel weight too but that doesn't vary depending on throttle.
Driveshafts a possibility but other possibility are engine mounts (but as they are active tend to throw a code)

I've checked the mounts in VCDS and both are fine.
With regards to drive shafts, the car is booked in with 4 Rings again this Thursday for them to look at everything in more depth.

Thanks for the help.

[longman h]

All wheel nuts tight ?
Tyre pressures correct ? 40-42 ish psi ?
All wheels still correctly balanced ?
All rims run true or are they warped/damaged ? a wheel balancing machine is the easiest way to check this.

All wheel nuts are tight, tyre pressures are OK, the wheels were balanced around a month/6 weeks ago but when the car was on the ramp last week, they mentioned the rear right tyre was out of balance so I'm going to try and sort that this week.

Tyres in good condition with no lumps of tread missing and not warped ?
Tyres matched up all round ?
Front tyres a match for 'El Knobbo' ?

Tyres are all ok with no signs of excessive wear and nothing from el nobbo. El nobbos have been removed.

curiosity , what tyres/sizes and pressures are you running?

Running Michelin PS2's on the rear and PS3's up front, 255/35 with I think either 40 or 42PSI.

all the above are the easiest cheapest things to check and sort out , if none of them help, then you can start working back though the drive train ..............and your wallet

The fact you mention that 10 miles away from home the vibrations had pretty much disappeared ,makes me think an oval'd/deformed tyre or rim as the culprit. the fact you've done a few miles since this started suggests the affected tyre/wheel has now worn down so it runs true , check for excessive wear on all 4 tyres. It also suggests under inflated front tyres, and 'el knobbo' has done its work , but you have been lucky and it hasn't gone through the carcass completely.

any play in any suspension arms and DRC ?
you also mentioned you was after a steering rack for a plus, this isn't related to the current problem is it ?

Car is on coilovers so no DRC issues and with regards to the rack, it hasn't been fitted yet.

Thanks for your help mate.