I've been driving our Peugeot 407 diesel today and it's way down on power. I haven't driven it for a long time so I don't know how long it's been like this. I put my foot to the floor at any speed and it accelerates very slowly, but over 40mph it hardly accelerates at all. It does have a small surge of power at about 2,000rpm so I don't think it's the turbo. The air filter doesn't seem especially dirty.

I did some Googling but I haven't found a lot that I could do without plugging in a diagnostic tool. I've tried unplugging the MAF, MAP, and EGR separately but none of them made a difference. I'm not sure if unplugging them is supposed to make a difference anyway.

Any ideas?

Hello a possible cause is the air flow meter, I'e had many of there go down at work so try a second hand one from a breakers 1st....Gordon

Boost hose comming of ?

Blocked fuel filter ?
when was it last changed?

Agree with above, check the hoses to and from the intercooler they do have a habit of splitting. HTH Ray

FWIW if it's the MAF you can identify this fairly easily by removing the MAF connection and driving round without it. If the performance returns along with the orange warning light it's probably that.

Also culprits are fuel rail pressure sensor faults, EGR stuck open and split boost hoses. I'm currently trying to get the boost hoses off my 306 with teh same engine but it's pretty well shoe-horned in and covered in oil so I'm in the "I don't care anymore, I might just leave it" camp.

Check all the hoses first

Lad at work had similar issues with his TDI Mondeo and it came up as a MAF sensor issue on the code reader
Did some checking and digging around and found a 4" split in one of the pipes

Split turbo hose is normally accompanied by a whooshing or whistling noise . Does it have a DPF?? could be blocked?

Thanks for the replies. There don't seem to be any hose splits but since I posted the thread it has started coming up with a "Depollution system faulty" message. That didn't come up when I ran with the EGR unplugged.

I've seen some suggestions about removing the DPF (Part of the exhaust?) and cleaning it out with water but that seems a bit tricky. There was another suggestion of using some diesel additive to clean the DPF out but they didn't say what kind of additive. I assume they meant something like Redex.

had that on my 2.0 hdi peugeot van....depo warning and orange light,low power and minimal revs.was told to keep in low gear and drive it for a few miles to blow out the particulate filter...not nice for those following the van.Its abalance of not cutting the engine through the ecu and progressively getting higher revs.Once blown out the light went out,on another ocassion had to reset through ecu.I honestly believe it was caused by a weeks driving very slowly due to ice and snow.

Sounds like the DPF isn't regenerating properly, a good thrashing may help . Various additive manufacturers do a product to clean a DPF but it may mean removing it to do the job. Removing the DPF and replacing it with a straight through pipe would probably mean reprogramming the ECU , there are companies about who can do it

Update: It was due for a service so we said about the loss of power when it went in. It turned out there was a split pipe on the EGR meaning the turbo wasn't spinning up. Total cost was about £180, half of which was diagnostics. It seems to pull harder than what I remember and there's a very definite kick at 2,000rpm now. I haven't driven it for months so maybe it's all in my mind. But then, the service report said it was a 163bhp model when it's actually a 145bhp... hmm.

Split EGR pipe? curious. The main EGR pipe is rigid metal so I assume they mean the vac hose that controls it. Pretty spectacular effect if that's the case. Might have to check mine