C4 HDI - NO BOOST AT ALL!

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wozzlegummich
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C4 HDI - NO BOOST AT ALL!

Post by wozzlegummich »

Not another bl**dy thread about turbo boost on a C4 HDI!

Long story but I really need some help understanding how my little beast works. I've done a fair bit of Googling here and on other forums but just can't find the answers to my problem.

Car is 2005 C4 HDI 1.6 Manual - Australian model no FAP but has a cat conv 90PS. The story so far... bought car cheap - knackered turbo & one piston. Rebuilt turbo, oil lines (fitted spin-on in line filter for turbo), oil pickup, piston, set of rings and big end bearings. Blocked off EGR. (For those really interested here is the whole story with pictures. http://goo.gl/QIY41i ) All fine till about 2 months ago boost dropped off to the point of being ZERO. Got a few codes come up about driveline & EGR. Cleared codes, no difference.

Replaced turbo again with brand new complete unit (old one had a fair bit of play in the shaft). Still no boost. Checked all the obvious things like leaks turbo plumbing etc. I've been watching various parameters via an app on my phone (Torque) and a bluetooth OBDII dongle. MAF seems to be working OK. Fuel rail pressure seems ok, boost shows ZERO or maybe 0.2 PSI at best but manifold pressure is stuck on 14.5PSI and goes to 15.5PSI when accelerating. It is still driveable (just very slow up hills) but fuel consumption is amazing returning 1200-1300KMS on a tank.

I'm to the stage where I really need to understand how the turbo/ecu/injection system interact. A few questions I have for the far more knowledgeable than myself.

1. Does the variable vane control actuator on the turbocharger operate with boost pressure or vacuum?
2. Is there a solenoid that controls the boost?
3. Is there a blow off valve that could be stuck open?
4. What is the difference between manifold pressure and boost pressure?

Thanks in advance for any help/discussion/answers - Robbie.
Peter.N.
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Re: C4 HDI - NO BOOST AT ALL!

Post by Peter.N. »

I don't know whether this will be any help at all but I have a problem with a 2.0. 8 valve Hdi that is using about twice as much fuel as it should be, I have had my newly acquired Lexia on it but am on a very steep learning curve at the moment.

I don't know if your engine is the same but there is a butterfly valve in the pipe between the intercooler and engine, I don't know what its for unless its part of the EGR system. When I saw it I was suspicious as the effect of it being stuck closed would considerably reduce the amount of air getting into the engine, the reference on the Lexia to the valve I think it is shows 88% and it hardly moves, I have looked at a couple of demo's on youtube on a 307 and its showing virtually 0%.

Its now dark so I have had to come in but I will be very interested in checking this function tomorrow.

Peter
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Re: C4 HDI - NO BOOST AT ALL!

Post by wheeler »

Peter.N. wrote: I don't know if your engine is the same but there is a butterfly valve in the pipe between the intercooler and engine, I don't know what its for unless its part of the EGR system. .
Your right its the EGR throttle butterfly & works in conjunction with the EGR system. As long as it stays fully open at rest best thing to do is to disconnect the vaccum pipe from it & block the end of the vac pipe with a small bolt. A deliberate restriction in the air intake is always going to be troublesome at some point. It can be left permanently disconnected with no issues.
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Re: C4 HDI - NO BOOST AT ALL!

Post by RichardW »

Robbie

The 90 works a bit differently to the 110 AIUI - it uses a waste gate rather than a variable vane turbo. However, it's still vac operated, and I expect there is a vac solenoid down the back of the engine. Post up the last 8 digits of the VIN and I'll have a look on service. citroen to see what it says.
Richard W
Peter.N.
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Re: C4 HDI - NO BOOST AT ALL!

Post by Peter.N. »

I have already disconnected the EGR in an attempt to improve the fuel consumption with no effect but I am going to do the same with this butterfly today - when I get back from a doctors appointment. Thanks for confirmation that it is part of the EGR system, I couldn't think what else it was.

Peter
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