R36 judder/vibration idle issue - cannot resolve

[JaysBlueR36]

Hi guys

R36 with roughly 200kms on clock.

On cold start up when the DSG is in Park the car judders and shakes intermittently sometimes more aggressively than others this will calm down but never fully goes away by any means. There is no chain rattle on start up.

These judders/shakes are felt in Park and Neutral only. In Drive, reverse and Sport the engine runs a lot smoother and you there are no unwanted sensations in the cabin. The car accelerates just fine and runs well, there is no hesitation or stalling.

Just to be clear there arent any vibrations that come through the steering wheel or gearstick. You feel them through the seat as they move through the chassis of the vehicle. They aren't particularly violent but the fact that they are makes me concerned about what may lie beneath.

The engine block feels firm if you try to move it when it's not running but definitely moves quite a bit when it's running especially when you first start it.
Also, I don't know if this is relevant but if you unplug the MAF while the engine is running the engine continues to run and doesn't cut out. It runs pretty much the same. Shakes can still be felt. Plug the MAF back in and the engine dies...

Recent work list
- injector clean and service
- intake runner check, clean didn't need walnut blasting
- aux belt pulley/tensioner/balancer check all good.
- coolant temp sensor replaced
- coolant leak fixed
- transmission mount replaced
- PCV replacement
- rocker cover gasket replaced
- intake manifold gasket replaced
- throttle body cleaned and reset
- oil service with 5W40
- compression test (all within spec)
- spark plugs and Coil packs checked by mechanic didn't see any issues.

I've spent lots of money and got no where. Kind of fed up and it's really annoying. Vacuum leak, mount issue, DMF - any help much appreciated

[kamold]

Any fault codes logged in ECU?
Misfire counters incrementing?
If there are misfires are they on specific cylinders, or random multiple?
If on specific cylinders can you move coilpacks and see if misfires follow the coilpack?
Don't think it would be dualmass flywheel if it's a noticable movement. That would just be a rattly noise. But maybe you're hypersensitive to it?

[JaysBlueR36]

No fault codes
There was a misfire on cylinder 2 which was a resolved with a new spark plug.
It had new OEM spark plugs and Coil packs in September last year (so they've only done about 3000 miles and there's no oil in the cylinders so they aren't fouled)

It is normal for the engine to move so much. It's shaking like it's become unbalanced in Park and Neutral then calms down considerably in gear. Drives fine but something isn't right.

How many engine mounts are there?

Is it worth changing the MAF and air filter?

[MMR36]

Hi, you didn't list it in your overview of work done above, but if you haven't checked the dog bone or pendulum mount, might be worth a look. if it's shot there'll be a lot of movement.

Cheers

[JaysBlueR36]

As far as I am aware it is okay. I will get it checked. Theres no clunk sound. I have had the transmission mount replaced but none of the others, how many mounts are there?

Anyone think it's worth changing the Crankshaft position sensor?

I'm considering installing a new set of plugs - but, using the original Bosch ones the engine was designed with and not the now OEM NGK ones. I will replace the Pipercross panel air filter with a normal one and the MAF too perhaps ( if someone can tell me if it's normal for the car to continue running when you unplug the MAF sensor? )

Is it worth replacing the fuel sender that has the inbuilt filter and getting the HPFP checked out?

[kamold]

There is an engine mount, trans mount and the pendulum (dogbone).
If you're not logging any faults it's unlikely to be a sensor or fuel issue.
Maybe post a video as it's very subjective especially from a written description.
Yes engine will run with MAF unplugged. You'll get a fault code obviously.

[MIG]

The mounts are pretty easy to swap. I did not notice a vibration with mine before replacing them, but it seems much smoother now.
I replaced mine as they had pretty much collapsed.

[kamold]

My trans mount was...well...totally flaccid.
No harm in replacing if it hasn't been done before.

[JaysBlueR36]

It's really difficult to catch it on camera vibrating it's so much easier to see in person. See what you think, clips only 6 seconds long.

VR6 running - YouTube

(When it's started from cold it can sound a bit like this) odd sound

Just to confirm no check engine light and no fault codes. I intend to replace the other two engine mounts and things like the PCV have already been done.

The idle is definitely just off, it's hesitant, instead of running smoothly it's a bit up and down like a heartbeat.

Also, I've worked out that if you unplug the MAF the car will continue to run and it doesn't really change in any significant way how it's runs, the engine just keeps going. If you plug the MAF back in the engine dies straight away. If you then start the engine with the MAF plugged back in, the engine will then run slightly different again and audibly idle a bit higher than normal... baffling - is this normal?

The battery is also the original so 15 years old. Needless to say I ordered a new battery and MAF today.

Generally, Help!

[MIG]

The vibration almost seems like a vacuum leak, any hissing noise near any of the pipes? It will be interesting to see how you go after the MAF replacement, it might be an unmetered air issue, hard to tell, not in person.

[JaysBlueR36]

I don't hold out much hope that the MAF will make a difference. Reason being is that if the MAF is unplugged the idle doesn't improve, when it's plugged back in and I start the car it will then idle higher on the rev gauge and its worse. It would be useful to know what a car without my issue and the MAF unplugged ran like!

I thought it was a vacuum leak too which is why I had the intake manifold removed, the throttle body out (and cleaned), a new PCV, new rocker cover gasket, new intake manifold gaskets, a new purge valve etc. Are there any common hoses that split on these or a way to help find one?

Either a hose has split and it's not been found or it's a fuel not a air issue but then the injectors have been done and there are no codes.

Also, there is the subject of the chain. It might be out.