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Discussion Starter #1
Our 2008 has developed an intermittent problem in that while driving, the engine can suddenly start rattling and running extremely roughly but there are no warnings on the dash.

The video link illustrates

Switching the engine off and on again, the car then runs fine. There don't seem to be any common factors about when it occurs and each time, turning the engine off clears the problem until the next time. It's occurred twice in the last week.The car has been into the local garage (not a Peugeot dealer) twice and they have run diagnostics both static and while the car is being driven and and can find nothing even marginal. Their opinion is that it could be something to do with one of the injectors, however they say there's little they can do, unless we can get the car to them while the fault is occurring.

I'm posting this in the hope that someone here might have experienced or seen the same

Thanks in anticipation
 

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Discussion Starter #3
Dodgy EGR valve is most likely culprit but there are other possibilities
Many thanks for that. I wonder why stopping and restarting corrects the problem, as if it was mechanical I would have thought it would still be there on restart? Having read up a bit a bout ERG valves (not knowing anything about them) I notice there are different types including Electronic vacuum-controlled EGR valve and Digital EGR valve, so I wonder if switching off engine is resetting something in the electronics? However I don't know what type of valve the 2008 has.
 

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Yes yours is electronic that's why I say it could be that as turning off resets it but it could be a bad injector too as both can produce the knocking noise this is the problem it's hard to say for sure.
 

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Yes yours is electronic that's why I say it could be that as turning off resets it but it could be a bad injector too as both can produce the knocking noise this is the problem it's hard to say for sure.
Thanks again. I presume the electronic system doesn't detect this issue, otherwise something would come up on the dash? The local garage reckon the only way they could check, would be to plug in their diagnostic computer while the problem is occurring, then something might show up. They say they could start changing injectors, but at something like £250 a pop, could be an expensive process of elimination. I'm wondering if a Peugeot dealer's diagnostics go any deeper? Presumably running the engine like this for any length of time can't be doing it any good?
 

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No unfortunately diagnostics wont show anything other than possible faults relating to the issue even when its doing it as it sounds like a purely mechanical issue and peugeots system wont be any better this is where people get confused diagnostics does NOT show everything and it also does not tell you the answer it is merely a tool that helps guide the way and even then its not always much use !

Sometimes reading faults leads you straight to the answer as you have seen it before even though it may not be directly related to the codes stored in your case i suggested the EGR as its the cheaper option and if it was me i would fit a blanking plate and run it see if issue goes away if it does EGR is causing it if it does not then injectors are most likely the reason.

I dont think peugeot would have much more luck than your present garage.
 

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Discussion Starter #7
I happened to have a transmissions engineer visiting today, and he suggested Dual Mask Flywheel? He reckons wear in the mechanism causes the flywheel to hit a resonant frequency which it can't get out of until the engine is switched off. To me this does make a bit of sense, no errors on dash, clears when restarting engine and I noted how metallic the noise sounded.
 
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