Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0

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Wed 7 May 2014 10:33
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - redmule
Had this problem for months. Car drives well, smooth, pulls okish in lower gears, but in 5th 6th it's very flat, up at 50mph, put foot flat on the floor and accelerates poorly up to 70 sometimes seems as if 70 is the max and won't go any more, it's been diagnosed twice by a Peugeot specialist and another garage , both stumped by it, no faults showed apart from Maf sensor which was replaced ,no turbo faults came up,no faults on dash , there's no whistling, no smoke, all very frustrating drives well, just flat .
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Wed 7 May 2014 11:59
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - Railroad.
Check all air intake hoses for security and leaks. Check turbo wastegate operation and EGR operation. The symptoms you are describing do resemble those of a faulty MAF sensor. With suitable diagnostic equipment you should be able to compare the ECM expected mass airflow against the actual airflow. This should help you to make a diagnosis.
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Wed 7 May 2014 12:56
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - redmule
Thank you for your reply.The peugeot specialist did a full live test of the new MAF sensor, and it showed an improvement, but did not heal the problem, he came up with no leaks in testing, and wastegate did not show as faulty on diagnosis.the only thing I haven't done is find someone who can test turbo pressure.
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Wed 7 May 2014 13:05
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - redmule
Is it possible a sticking wastegate would not show up on the diagnosis?
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Wed 7 May 2014 14:03
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - Railroad.
If you had a sticking wastegate then you could have a potential overboost situation. In this case the ECM will reduce engine power before the excess boost destructs it. This could be the loss of power you are experiencing, and is a safety protection, not a fault itself.
If the wastegate was stuck open you would have a loss of turbo boost. The ECM may not recognise this as a fault because a loss of turbo pressure would also mean a reduction in airflow, and the ECM wouldn't know the difference between that and gentle driving.
To understand why the ECM does what it does you really have to switch off your mind to reason and think like a computer. It's a dumb machine that does EXACTLY what it's programmed to do. No more and no less.
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Wed 7 May 2014 15:08
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - Gibbo_Wirral

What's the condition of the air filter housing? I've found on a few occasions on the 407 that the lugs have broke and it lets in air through the gap. Many owners add a self-tapper into each corner to keep it together.


Have you tried driving it with the MAF sensor connector unplugged? You'll get an "anti pollution fault" on the dash but it shouldn't go into limp mode.

Edited by Gibbo_Wirral on 07/05/2014 at 15:09

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Wed 7 May 2014 20:54
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - redmule
The air filter housing all looks good, nicely sealed. I did try unplugging the MAF a while back and anti pollution fault did light light up, and no limp mode, didn't make a lot of difference to be honest.
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Wed 7 May 2014 20:49
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - redmule
Yes i see , that all makes sense, maybe it's the wastegate actuator at fault.do you get some boost if the wastegate is not working, because I'm sure it terrible to drive with zero turbo?
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Fri 8 Aug 2014 22:10
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - lenni1402

Hi Redmule,

I'm from Holland and have a similar problem that you have or had. The peugeot dealer can not the solve the problem. I have done a lot of testing and i can not trace the problem. Tested the injectors, maf sensor turbo valves but i still have the problems.

My question is: is your problem solved, and what was the solution or what parts where changed?

With kind regards,

Lenni from Holland!

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Thu 4 Feb 2016 18:08
Peugeot 407hdi 2.0 - Lacks power peugeot 407hdi 2.0 - redmule
It's only taken 2 years and a new turbo , but I have finally solved the problem , after having the new turbo fitted and it not fixing things , I went looking and found a broken connector on a vac line, it was round the back of the big turbo pipe so not easy to see I fixed it together with some tubing I found ....it didn't work, so thought that was not the problem, spent another month with the endless head scratching, then decided to go back to the vac pipe and do a better job with some better tubing, .....got in the car and wow.... Sudden power....amazing ....goes like a rocket after years of no power, couldn't believe two garages never spotted the broken vac pipe.!!
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