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Hi,

Since a few weeks I am the owner of a Cayenne S 957 4.8 from 2008. But I notice that the car struggles to start after standing a few hours.
When I try to start it in the morning it takes a few seconds to start and then it idles quit rough. It seems to misfire in some cylinders. When I press the accelerator to 2000rpm for a second or 2 it goes to a "normal" idle and the shaking and rough idle are gone. No error codes are shown on the dash or Piwis tester.
There is no unusual noise coming from the engine and it had a new battery last week (unfortunatly that didn't fixed the issue).

Anybody who had the same problem before and has any ideas how to fix it? It drives great it is just the rough idle at cold start that is not right.

Kind regards

Tom

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Unfortunately, without codes or other "real time" data capture from the vehicle, this is rather difficult to diagnose remotely.  Is it possible for you to capture data while this is happening?

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It doesn't have to throw codes to run poorly, we see cars from time to time that were barely running, but free of codes; these are what separate those that understand diagnostics from those that throw parts at the problem.

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On 7-7-2017 at 4:33 PM, JFP in PA said:

Unfortunately, without codes or other "real time" data capture from the vehicle, this is rather difficult to diagnose remotely.  Is it possible for you to capture data while this is happening?

I took pictures of the engine data before and after starting the car. What data should i upload here?

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It seems like my actual value is following my setpoint high pressure value when driving or idling. But only after the rough running is over.

It doesn't keep the high pressure in the rail, i only got around 4 to 5 bar when the car is turned off. I believe it will be a valve in my HPFP as the low pressure (which should be around 5.5 bar) is maintained (it is normal to drop 1 or 2 bar in a couple of hours).

 

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