TDCi judder around 2200-2700rpm

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Tue 15 Aug 2006 11:44
TDCi judder around 2200-2700rpm - bobda
I'm experiencing a judder between 2200 and 2700rpm (roughly). It occurs on light throttle and is most noticeable at motorway speeds (70-80 mph).

It feels like the car slows down, then speeds up again slightly and sometimes it judders in waves, which always occurs at about 2500rpm. It still does it when the cruise control is engaged, but not as badly. This is probably due to the ECU counteracting the loss in power by adding more fuel and 'smoothing out' the problem.

It's done nearly 70k miles and has recently had a new turbo fitted (old one went blew a seal and dumped oil out of the exhaust) and the garage who changed the turbo nd fitted a new exhaust, said that they had fitted a new EGR valve, but I'm not 100% sure if this was done. It has also had a custom remap, but this was fine before the turbo went pop.

I've tried cleaning the MAF with Isopropanol, which didn't cure it, but the hesitation feels almost like a MAF fault, as if it is telling the ECU that there is more air getting in than actually is and less fuel is consequently injected.

Anyone got any suggestions for other potential causes?

It's a 2002 Volvo S40 with a Renault DCi (surprise surprise) engine.
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Tue 15 Aug 2006 12:00
TDCi judder around 2200-2700rpm - cheddar
Sorry cant help though perhaps the mods can amend the title to say "Volvo S40 1.9d", it currently indicates that it is a Ford.
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Wed 16 Aug 2006 00:59
DCi judder around 2200-2700rpm - bobda
Does it? Sorry about that if it causes confusion.

Bit more info...it only seems to do it when the engine is warm/off choke, so I'm pretty sure it's something to do with the fuel delivery.
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Wed 16 Aug 2006 20:06
DCi judder around 2200-2700rpm - Screwloose
bobda

DCi's don't often survive a blown turbo unscathed, particularly if [the usual] compressor turbine failed and bits went through the engine, or there was a runaway. Have your garage done a compression test? Other than that; the whole EGR system is very high on the list of probabilities. Things like faulty injectors, [done a leak-off test?] cam timing and even flywheel issues can't be ruled out.
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Wed 16 Aug 2006 23:30
DCi judder around 2200-2700rpm - bobda
The turbo failure was a seal that blew, which dumped oil through the turbo. There wasn't any runaway, I just lost power in a cloud of white smoke and stopped on the hard shoulder. There was still oil left in the car on checking the next day and I didn't get an oil pressure warning.

As far as I can gather, nothing went through the engine apart from oil.

I'm going to have a look at the wastegate over the weekend, I've got a feeling it may be at fault since there is an escaping air noise that appeared before the turbo went pop and the turbo doesn't seem to be 'following through' on changing gear, as if it is losing pressure all the time.
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Thu 17 Aug 2006 01:06
DCi judder around 2200-2700rpm - Screwloose
bobda

Turbos don't have oil seals in the conventional sense, so they can't "blow" unless there's a build-up of pressure in the crankcase[??] Escaping air usually means a failed ducting hoseclip or a bulged/split intercooler [a Laguna DCi speciality.] That might fit your odd symptom. Look for leaking oil mist traces. An intake leak, causing a turbo overspeed, might be a very likely reason for the initial turbo failure.
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