2.0 TDI PD - engine vibration advice please

[AndrewW]

Having read a large number of posts on the forum about possible causes, I thought I would see whether I could gain concensus on the problems of my 2004 Octavia II 2.0 TDI PD with 65,000 miles on the clock.

Symptons:

- About 1500 miles ago, applying gentle acceleration to increase speed when travelling in any gear between about 1700 rpm and 2100 rpm caused a juddering vibration. Not unlike bad pinking in old fashioned speak.

- Now, engine noticeably rough at idle (both from cold and when coming to rest after a long motorway run and irrespective of clutch in or out) and the juddering now occurs from about 1600 rpm to 2400 rpm on gentle acceleration.

- No problems when accelerating away from rest irrespective of gentle / hard acceleration.

- No problems when driving more enthusiastically at any enginer revs (or gentle acceleration above 2500 rpm)

Diagnosis to date:

- Taken to garage 1500 miles ago - no faults showing up on their diagnostics.

Thoughts on possible causes:

- Dual Mass Flywheel (but problem doesn't seem to occur when accelerating away from rest - is this significant?)

- Engine mounts (notable that CamBelt replaced Oct 2008 with no mention of engine mount bolt replacement - but that was rather a long time ago so I don't think it's that relevant in case someone asks the question)

- Something upsetting the electronics that doesn't show up on the diagnostics (e.g. corrosion in any one of numerous connectors)

I note from recent postings that it is theoretically possible for the garage to check the DMF without taking the gearbox off, so this is probably a good option to check out. However, any advice on possible causes (including other causes not included) would be gratefully appreciated since it does seem to have got worse in the last few days.

Many thanks

Edited 31 May, 2010 by AndrewW

[psycholist]

Rough idle with the clutch in says it can't really be the DMF. Try a wodge of silicone grease in the MAF plug (See 'cage mod' for more info). Also worth trying to reset the car ECU. I think unplugging the battery for more than a minute will clear the ECU back to factory settings, so if it's mislearned how to run the engine over time it'll be reset.

[AndrewW]

Rough idle with the clutch in says it can't really be the DMF. Try a wodge of silicone grease in the MAF plug (See 'cage mod' for more info). Also worth trying to reset the car ECU. I think unplugging the battery for more than a minute will clear the ECU back to factory settings, so if it's mislearned how to run the engine over time it'll be reset.

Thanks for the rapid response - interesting thought that it can't be DMF if clutch position is irrelevant on idle..

The MAF Plug / Socket (which I think is the large one at the top of the engine) is clean with no signs of corrosion - while I haven't done the silicone grease trick, I have mated/unmated plenty of times to make sure that the contacts are making. Also, it's dry here at the moment so I don't think it is that.

I've tried your suggestion of disconnecting the battery - left it for at least 5 minutes. Unfortunately, no change on idle so I didn't attempt to take it for a run.

Keep the ideas coming - I'm willing to try things within my limited capabilities!

[Eivind]

Have you tried any diesel aditives? Mine is juddering now and then around 2000 rpm, and I throw in a bottle of tunap or wurth injection cleaner.

[swil00]

I've had similar problems in the past with mine, one of the dealer visits saw the car remaining with them for a day short of 4 weeks.

Is the juddering quite violent ? Mine was and I found the car very easy to stall when pulling away with little or no revs. juddered around

the same RPM's as you mention, but mine would cut out under load pulling away at times...

After several dealer trips, eventually diagnosed to a Crankshaft sensor....... 14k later and all is still well !

I'm no expert by any means, be from experience, Possible causes:

Injector(s)

Injector loom

Crankshaft sensor

[cheezemonkhai]

Rough idle with the clutch in says it can't really be the DMF. Try a wodge of silicone grease in the MAF plug (See 'cage mod' for more info). Also worth trying to reset the car ECU. I think unplugging the battery for more than a minute will clear the ECU back to factory settings, so if it's mislearned how to run the engine over time it'll be reset.

I disagree, the DMF is always attached to the engine so you can get the vibration with or without the clutch engaged.

Try getting the EGR valve, intercooler and the throttle body cleaned out and reset as this might help.

Edited 1 June, 2010 by cheezemonkhai

[AndrewW]

Thanks to everyone for their replies. The point from cheezemonkhai about the DMF always being connected to the engine is sobering from the perspective of the £1000+ it costs to sort that out (although I'm still trying to work out what a "mad midget trying to hammer his way out of hell" actually sounds like :wonder: ). I'm attracted to the crankshaft sensor, although I don't feel that the engine is about to stall on me when setting off but it does feel reasonably violent to the extent that I lift off and change down a gear.

I'll try to source the diesel additive today on the basis that it can't do any harm - presumably I will need to run that for a few hundred miles before I see a difference.

All the advice being provided goes to prove that, in the absence of a definitive fault code, it is pretty difficult for a Garage to diagnose the problem without replacing parts (and potentially a lot of parts). I'll have a chat with my local Garage (Garlands in Aldershot) during the week - I've always found them reasonable, but it had them foxed a month ago so the list of suggested items to look for should allow some prioritisation to be done, starting off with another diagnostic hook-up in case something is now showing; then checking the DMF through removal of the starter motor or the inspection plug (if my 6-speed manual is an "02m"); then clean out / reset of EGR valve, intercooler and the throttle body; then Crankshaft sensor; etc.

I'll post an update with progress as and when it happens. Thanks again.

Edited 1 June, 2010 by AndrewW