Engine vibration, misfire or DMFW?

[PJS4Avant]

Hi all,

Long time lurker, first post. I have a 53 plate S4 avant @ 64k miles that has suffered from an engine vibration around 3000rpm upwards. Initially I thought a coil pack or engine mount may have failed but after 2 days I came around to thinking the dual mass flywheel had failed instead. What was really strange is on the 3rd day the vibration had disappeared, completely. The clutch has felt normal throughout and I have seen no engine check light.

My question is for the owners who may have experienced a similar vibration, what was the end result? I am a motorsport mechanic but this has me perplexed! I realise a diagnostic check will tell me if a coil or engine mount has failed. How much vibration does a failed coil pack produce on a V8? I guess considerably more than an in line engine? Financially I am really hoping it is not the DMFW.
Today was day 4 and still it feels fine.

All comments welcome

Cheers
PJ

[gottanS]

Hi PJ,

Not experienced what you have described but there was a post on this section a while back about something similar IIRC and that turned out to be the alternator I believe. Worth doing a search and see what pops up.

Pete

[infrasilver]

I had an engine mount go in the summer and that gave no vibration at all but it was only the electronics gone. The reactive mount had stopped reacting basic-ley.
I would be surprised if the rubber was gone @ 64,000. They are a big lump of rubber and metal.

[PJS4Avant]

Thanks for the replies, i'm now on day 5 and still the vibration hasn't come back. struggling to get my vag-com lead/software to work so will find out what's going on at APS in Brackley next week. Fingers crossed!

PJ

[marv]

I'm pretty certain that a duff coil pack will result in the engine light coming on, as well as a pretty noticeable misfire wobble. My engine light certainly came on when one of my coil packs went.

[Stalex]

I had a coil pack (at least 1) go in france whilst on holiday this summer. The engine management light came on immediately and the car ran like a dog, stuttering power delivery unless under full acceleration, which seemed to cure the stutter, for some reason.

[PJS4Avant]

Hello again,
The vibration is back, same as before and I am still thinking DMFW. Has anybody experienced a DMFW failure with the vibration coming and going? This time the vibration came on last night on the way home from work, this morning I took it to a respected independant specialist where they also believe it to be the DMFW then blow me down, on the way home the vibration disappears again. I'm reluctant to spend £2k on a DMFW and clutch without being 100% sure of the fault.
Please help.

Cheers
PJ

[Ian_C]

To be fair, plenty of owners have got through a clutch in less than 64k, your mileage in Dec which has no doubt grown since. My clutch and flywheel were done coincidentally at 64k. If you bought yours recently no doubt you factored in a clutch and flywheel into the running costs anyway. Any signs of slipping when hot after you floor it from a steady speed through the meat of the torque band in higher gears?

Ian

[PJS4Avant]

Ian, just to be clear the clutch isn't the issue. There is no slip and everything feels normal. I only included the clutch in the job as it makes financial sense to change it while the gearbox is removed. As to the life of a clutch I believe it is completely dependant on the work done and abuse it's given rather than a certain mileage. Why did you have both the clutch and DMFW changed together? Did you have a worn out clutch which damaged the flywheel?
Cheers
PJ

[Ian_C]

Merely a suggestion. Yes, like all cars, it depends on use, abuse, stop-start journies etc, but generally S4 clutches don't last long. Being approx eight hours labour to get at the DMFW or clutch, as you say yourself, everyone replaces them together. No idea which was the 'cause' on mine, it was done before I bought it, and I purposefully tracked down an example that had a fresh clutch and flywheel to save myself the time and bill.

Ian

[BlingBling]

but generally S4 clutches don't last long.

How do you come to that conclusion? I have owned my car for 5yrs (68k), been a member of many forums and have never got the impression from these forums or through ownership, still original clutch, that they "generally don't last very long"

Abuse the clutch and it won't last long. Drive the car sensibly and it will.

[nihc]

Hi.

There was an Audi TSB about loose inlet manifold bolts in pre 2006 cars, IIRC.
The TSB states that the torque should be checked on the bolts.

If you have loose bolts it can give rough running and usually a misfire.

It's worth checking the bolts for tightness - there easy to get at.

Thought I'd throw that in, as it's worth checking.

[PJS4Avant]

Hi All,
Just got the S4 back after its had the new DMFW, clutch and slave cylinder fitted. Feels great, no vibrations, much smoother and a lighter pedal. I didn't think it would make as much difference as it has to the driveline shunt and although it was the vibration that pointed to the DMFW it was obviously well worn and not dampening as it should. For reference they fitted the later B7 clutch. Expensive, but it had to be done. Good service as usual from APS.

Cheers
PJ

[xyber]

From what I gather the flywheel was updated on the B7 to cure a problem with it separating, so if you fit that flywheel you have to use the B7 clutch.

[PJS4Avant]

From what I gather the flywheel was updated on the B7 to cure a problem with it separating, so if you fit that flywheel you have to use the B7 clutch.

Xyber,

Not sure about that as APS reckon the Audi part number for the flywheel was the same for the B6 and B7?

Cheers
PJ