Clatter from transaxle??
 

Just did my IMS in my 2002 Boxster S and after putting everything back I've got a low idle clatter and noticble vibration from the drivetrain. Engine revs fine and with the clutch in the noise goes away but is still there slightly.

Sounds like it is coming from the transaxle and more near the rear than clutch. Could I have broken the gearbox somehow? Seems to go into all the gears fine. When pulling off in 1st gear at low idle the drivetrain vibrations are fairly severe.

Any clues?

I will try and upload a video too.

okay so this is a video of the noise... it seems to require warm-up for this to get that bad and when cold, there is no noise, but in about a few minutes it starts...

https://youtu.be/OB884K-ugMI

Doesn't sound good.
I'd be taking that apart again to make sure the whole clutch assembly & throw out bearing were put together the right way and all fasteners were torqued to spec.

Yep, I'm thinking the DMF might have broken. Annoying to now reverse what I've just put back together, but good news is that I now know the steps!

are you sure it is not an exhaust leak ?

Yep, not an exhaust leak. Sounds like gears clattering and have read a few posts on forums that mention broken/failed DMF will cause that, as it is the back/forth motion of the flywheel causing major vibrations in the drive train. She sure sounds sick and drives poorly.... :confused:

Anyway, won't know until I tear it down again.

Any other clues or thoughts?

Man, don't drive with that. Disassemble and check for the cause.

Also don't do silly videos from above the car. Put it it on a lift and check where the noise comes from.

Regards, Markus

Thanks. I was already on that page, and the car is now back in the garage.

So I take it you don't have any better advice than "check where the noise comes from" ??? I was hoping the more technical and mechanical folks might have a thought as to what to look for - maybe that noise sounds like something you've heard before etc. If not, then yeah, I'm good with how to diagnose further.

When I figure it out, I'll report back so that someone in the future (with a similar fault) will be able to search and find this. I know this has helped me before when trying to diagnose possible issues.

G

Markus is correct.
You need the microphone close to the source of the noise.Otherwise people like me who rebuild an M96 and a G86 and therefore could help you ,think the noise is exhaust. Unsubscribed but suggest you watch the LUK video on DMF to see how to check it. I have linked it many times in Search.

Yes agree. Will do that and come back. Will try and get more audio of where the noise is coming from vs where it is not etc.

I've seen the DMF videos and know about the 15mm test and I'm now wondering if I was too keen to give it the green light when it was probably close to failure (or had failed).

Does the back-n-forth clatter of a failed DMF sound like (or would sound like) what my video sounds like? Thinking that the gearbox is clattering due to the rotation back/forth of the input shaft. When the clutch is engaged, the noise goes away, so seems plausible.

G

Quick update - figured out that the problem is probably too low idle, or at least that's why it is doing it when it warms up... when hot/warm engine is idling at 650 rpm !!!

That's not right and the noise/clatter goes away as soon as the idle rises above 750rpm. I think the standard idle speed is around 800 right?

So my guess is that I've got an air/vacuum leak or something like that. I wish Durametric has a simple AFR value that you can poll to figure out if the AFR is wrong for idle (confirming the air leak)...

Any other thoughts??

Idle speed spec for a manual trans car is 790 RPM with the AC off, 800 with the AC on. Tip cars are 790 RPM for either.

As your car is an egas version, the idle speed is controlled by the DME and therefore not adjustable. So if it is idling at 650 RPM hot, you need to be looking at why it is idling low.

You can use the Durametric fuel trim values to determine if it is either lean or rich:


The key to the adaptation values is as follows:

RKAT = Adaptation in range close to idle Cylinders 1 - 3

RKAT2 = Adaptation in range close to idle Cylinders 4 - 6

FRAU = Adaptation in lower load range Cylinders 1 - 3

FRAU2 = Adaptation in lower load range Cylinders 4 - 6

FRAO = Adaptation in upper load range Cylinders 1 - 3

FRAO2 = Adaptation in upper load range Cylinders 4 - 6

FR = Oxygen sensor for cylinders 1 - 3

FR2 = Oxygen sensor for cylinders 4 - 6

You can also use the Durametric to check the MAF values to make sure they are in line as well.

Thanks JFP!

So what are the expected MAF values at idle?

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