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Discussion Starter #1 (Edited)
Hi my 2.0 hdi 407 seems to be slow in upper gears only. It's fine driving about town in lower gears but getting on to the motorway it seems to have no power in 4th 5th or 6th. Any ideas? It still gets to high speeds but takes an age to get there and really struggles with hills on the motorway to the point where I may have to change down. I have checked and replace the airlines going from the intake to airfiler to MAF then into block and they are now fine and properly sealed (there was a crack in a pipe before...) but that doesn't seem to have solved the problem. To explain the symptom more I go onto the motorway, put my foot down in 4th say and it pulls away fine up to say 2k revs then it's like a massive dead spot. I put my foot down more and nothing happens.
 

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Most likely causes are MAF faulty or vacuum being lost and turbo solenoid is not controlling boost properly NO VAC NO BOOST
There is also a repeat sensor on the turbo this can cause lack of boost as its not sending the readings back to ecu properly.


Needs a session on planet to look at readings not just read codes.
 

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Discussion Starter #3
Most likely causes are MAF faulty or vacuum being lost and turbo solenoid is not controlling boost properly NO VAC NO BOOST
There is also a repeat sensor on the turbo this can cause lack of boost as its not sending the readings back to ecu properly.


Needs a session on planet to look at readings not just read codes.
Very grateful for your response. I bought the car thinking it was just an air leak as the pipe going from the MAF to the back of the block was broken. I've replaced this and it made no change so I am now looking elsewhere. The car is going in for a service at my local that I've used for years so I will ask them to look for any air leaks under the car whilst they do the oil drain and the bottom engine covers are off.
 

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You misunderstand its not an air leak its a vacuum leak IE the vacuum is being lost somewhere there are various pipes coming from the brake pump and this creates the vacuum to control various parts including the turbo.

You wont see a leak unless the pipe is obviously split or has come away from its fitting you need a vacuum gauge to test the vacuum levels as it is a very small amount.
 

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Discussion Starter #5
Hmmm followed some of what I think are vac pipes and these two in front of the engine block aren't even connected to anything! I can feel the two pipes that these slide onto, question is, which one goes to where. One has a plastic t-piece connected to it. Could this be the problem?
 

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Discussion Starter #7
Yeah found it now following the diagram... Big difference. Must have been affecting the turbo, pulls like a train now... wonder why someone would disconnect them???
 

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Discussion Starter #10
Can u circle where this is on the engine. I too have the same problem.
Thanks
Thomas

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See that green electrical connector on the top. right in the middle of the picture at the front of the block. It's kind-of under the left hand side of there.
 

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Its only there on this engine in the 407 on other vehicles with the same engine it can be in other locations.

If its not this engine then it will definately be elsewhere
 

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It's a 407 I have here anyways so will defs get a look tomorrow. Snowing here today in n.ireland.......no garage,no looking!!! On a lighter note 'dual heater' flaps, failed on drivers side......so freezing hand also!!!!?

Thanks peps.

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Discussion Starter #13
Just as a bit of advice, if those pipes have been off for a while, would it be advisable to disconnect the battery for a bit to kind of reset the ECU or to a soft reset? I had an old mondeo once that whenever we did anything to the fuel system, air lines etc we reset the car to sort of re-learn how the car was running.

Also as a side question... if you disconnect the battery on these... do I need a code to get the radio to work again? That's why I haven't disconnected it whilst doing any work on it as I wasn't sure...

I do appreciate all your advice. It's much appreciated and is helping me get this great car better again. I'm loving it so far, don't think I've driven such a comfortable motorway cruiser.

Rob.
 
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