2.0 HDi - No Boost

[cancunia]

My '05 2.0 Hdi has no turbo boost, or at best it's mostly no boost but feels every now & then as if there's a bit of boost. I've put the fault code reader on and can see no related faults, using Torque I can see there's just an odd flicker on the boost readings when I rev the engine but none at all when I went for a short test drive.
I'm fairly sure I can hear the turbo spinning up & guess I'd know it from other noise & smoke symptoms if the turbo had failed.

Is this a common / easy to fix fault?

Thanks.

[jj9]

I take it you have checked all of the air pipes etc to make sure they are sound.

Turbo waste gate operating ok, nice and free?


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[cancunia]

I take it you have checked all of the air pipes etc to make sure they are sound.
Turbo waste gate operating ok, nice and free?
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TBH, not checked anything yet as I was hoping to get an idea of how it all works. I've never worked on a turbo before so it's all new to me.

As a total guess, I think it's a wiring problem but again, without knowing where to look...

[polar]

Unplug the MAF and try it - they rarely though up a fault code. if it is better with the MAF unplugged you have found it.

Like JJ says visual check everything + fuel and air filter - start simple

[cancunia]

Unplug the MAF and try it - they rarely though up a fault code. if it is better with the MAF unplugged you have found it.

The MAF readings are ok so far as I can tell from using Torque & the OBD dongle.
Seems a mystery as to how the turbo is actually controlled. I will check the pipes, just be nice to know how it works. :-)

[cancunia]

OK, it runs a lot better without the MAF! I unplugged it this morning before going out and it's like night & day, so I have a dodgy MAF. I'll try cleaning it, but wondered if anyone just leaves theirs disconnected?

I did some more reading about the turbo and exchanged a couple of emails with Steve at HDI Tuning. Seems that the turbo on the 2.0 HDi does not have any variable boost, it just spins up and opens the waste gate at about 14psi via a pressure valve. There's no boost monitor either AFAIK, it uses the MAF to calculate boost & EGR.

[jj9]

So with the MAF unplugged do you have boost?

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[polar]

Sounds like you have a faulty MAF - not unusual on the 2.0hdi - advise get a good one from GSF or dealer as loads of crap ones on ebay.

[cancunia]

Sounds like you have a faulty MAF - not unusual on the 2.0hdi - advise get a good one from GSF or dealer as loads of crap ones on ebay.

Yeah, like you say probably a dodgy MAF. The car goes really well without the MAF and may even be at the root of the EGR problems I've been having.

Strange thing is that the MAF readings show up on Torque and vary in line with the revs, perhaps the readings are high/low & out of spec. I think it's time for some more investigation with Mr Lexia before buying a new MAF.

[jj9]

Not saying the MAF isn't your problem but unplugging it will set a default map so the fact that the engine runs better with it unplugged isn't conclusive proof.


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