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Discussion Starter #1
Hello all,

I have a intermittent fault with my 407 whereby if it is cruising along at 70 on a FLAT bit of motorway (not having to pull up a hill, not coasting down one) then there will sometimes be a slight surge, release, surge, release, surge, release, ... cycle which alternates back and forth between the 'surge' and 'release' one a second.

A few days ago this started happening whilst driving around town and made me wonder if it was going to make it home! A friend plugged on his Snap-On diagnostic tool and all he could find was a code on the fuel pump which was described, rather quaintly, as "implausible". Aside from the curious turn of phrase (odd translation from the original French, perhaps?) there were no other clues and, naturally, when we took the car out it behaved perfectly. Also, when diagnostic machines have been on this car in the past there have been no similar fault codes, even though this mild surge problem has been around for a good few months now. I wonder if the bad surges of a few days ago finally triggered the code.

Diagnosis from my friend was that it could be:
- bad fuel pressure sensor
- bad fuel pump
- bad injector leaking fuel and causing the pump to work harder
- any or all of the above

Anybody else feel like adding some suggestions of causes and/or recommendations for a course of action (not helped by the fact that it's not doing it again ... yet).

All suggestions gratefully received. Feel free to throw in amusing fault code descriptions you may have come across too!

Thanks in advance,

Angus
 
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For the surge release I'd suspect egr, easy enough to prove and/or blank, there's a thread on egr blanking in the 407 section.

Peugeot Planet owner, Doncaster
 

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Discussion Starter #7
For the surge release I'd suspect egr, easy enough to prove and/or blank, there's a thread on egr blanking in the 407 section.

Peugeot Planet owner, Doncaster
Thanks. I'll look it out and try it over this coming weekend.
 

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My next suggestion was EGR valve, I had an issue with an air leak on my older 407. It made it seem like it was on a boat sometimes, it was damn frustrating. It needed a new fuel filter housing. There was a very faint hairline crack in it, from either age or maybe an accidental smack with a tool of somesort.
 
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