No Boost, Exhaust Warning Light & Overboost - ideas?

[martinch]

Hi guys,

My relatives have a 2005 2.0TDi (PD140) Octavia. They were giving it a "bit of a push" down the motorway at the weekend to give it a bit of a clear out, as it only normally gets "pootled about" to and from work, and it decided that it wouldn't rev above ~3k revs, or do more than 60mph - apparently, it felt "like a normal diesel" (rather than a turbo-diesel).

An orange warning light for the exhaust system has come on on the dash (so I'm guessing the above behaviour is "limp mode" because of it).

Also, a scan with my fault code reader gives a DTC #16618 ("Boost Pressure Regulation: Limit Exceeded (Overboost Condition) : P0234 static-no define). I've also done a "readiness scan", which says:

MIL Status	On
DTC Number	1
Comp Component	PASS
EGR System	PASS
Fuel System	PASS

Any ideas what it could be before it goes back to the garage under warranty?

Thanks

[suk]

Sticking vanes on turbo mate, you will probably find if you knock ignition off and on again the fault clears for a while but that will be youre fault! Either a strip down and clean of the turbo, new turbo or a cleaner put through the turbo to get rid of the crap!!

[martinch]

Thanks.

Have tried the "restart the engine" trick, and the fault persists. It did this a couple of weeks ago (minus the light on the dash), and it looked like it was due to the large hose at the front of the engine (not sure what it's proper name is, but it's about 4" diameter) having "dropped" slightly on the lug (about 1-2 fingernail thicknesses) - a reseating and clear of the error (which wasn't static) seemed to fix it that time (or given this, mask it for a while).

Will have a look at the cleaning route, I guess.

[r32]

I've just posted about this issue with my 140tdi too. See here.

Costs wise, its looking like £700 for a reconditioned turbo, or around £1400 new from Skoda.

There is a cleaning kit out there, but the two independent vw garages i've contacted both said this would probably not work :(

[mikel543]

+1 for the sticking VNT Vanes on the turbo. Think somebody attempted DIY cleaning on here in the past, but can't find the post, IIRC correctly it had piccies as well.

Might be worth checking that hose again, maybe it came loose due to the overboost. Worth getting someone with VCDS to reset the fault codes and then do some logging on requested boost vs actual to aid in diagnostics before you shell out for a new turbo.

As an afterthought could be a stuck N75 valve, does the MIL come on as soon as turbo spools up or does it give some boost and give up? Worth a look at the N75 though as will be a lot cheaper than a recon turbo.

[martinch]

Thanks guys - guessed it might be the vanes as the fault code reader said EGR's fine, can't find any holes or flaws with the boost pipe, and it's not doing police car impressions, which tends to limit the possibilities (unless I missed something, which is quite likely! ).

The supplying dealer's had a look at it, and they think it's the actuator rod sticking, although they want it back again to have a further look and be sure.

The car's under warranty, so rather hoping not to have a bill on this one!

+1 for the sticking VNT Vanes on the turbo. Think somebody attempted DIY cleaning on here in the past, but can't find the post, IIRC correctly it had piccies as well.

Not this: http://pics.tdiclub.com/data/500/Drivbiwire_VNT_repair_procedure_small.pdf ?

As an afterthought could be a stuck N75 valve, does the MIL come on as soon as turbo spools up or does it give some boost and give up? Worth a look at the N75 though as will be a lot cheaper than a recon turbo.

Is the N75 valve the EGR valve..? Or..? I think from what was said, the MIL light came on after the turbo had spooled up (around or a little above 3,000rpm).

[Miss George]

I had same problem with the passat I used to own it was mass air flow sensor. You can by pass the turbo to check if it is the turbo before you waste the money on buying a new one.

Also on the passat I removed the pipe off the EGR valve due to it being a prone problem with the engines and she never had trouble.

[martinch]

Hi guys,

Just an update - the supplying main dealer had a further look at it, and replaced the turbo for a new one under warranty. Took a while (was done last week) as Skoda had to come out and OK the work.

Thanks for the input.