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Hi everyone, I have a slightly irritating issue that has been ongoing for a few months now. Having driven this car for several years, normally its idle RPM is 800. However, for several months, the car is having intermittent periods of high idle at 1000 RPM and at times the idle can be slightly rough. The car has no fault codes on my Autel machine. The DPF values before and after the latest regeneration that happened this Tuesday were: Before Latest Regeneration Km Since Last Regeneration - 417.1Km Soot Mass Measured - 0.21g Soot Mass Calculated - 24.26g Oil Ash Volume - 55.3341711g Oil Ash Mass - 55.3341711g Ash Load Limit - 70g After Latest Regeneration Km Since Last Regeneration - 2.5Km Soot Mass Measured - -5.57g Soot Mass Calculated - 4.68g Oil Ash Volume - 55.3402682g Oil Ash Mass - 55.3352631g Ash Load - 70g When the car initiated this particular regeneration, a grumbling sound came from the engine bay which I had never heard before but it has not happened since. Having done some research, I am suspecting one of the following: Bad DPF differential pressure sensor/blocked DPF - unlikely as the DPF is regenerating every 415Km or so which I believe is fine Bad alternator - unlikely as there is no battery warning light and the voltage of the battery during idle is 14.5V Weak battery - again unlikely as there is no battery warning light Fuel injector issue - unlikely as there are no engine fault codes and the car is not misfiring Bad thermostat - unlikely as I fitted a new OEM thermostat from Audi in Nov 2023 Bad coolant temp. sensor - possible as it has not been changed, over the past week when motorway driving, the temp. gauge on the dash was fluctuating between 70 and 90C instead of staying at its usual 90C Also, over the past week or so, there has been an extra sound coming from the engine bay (I believe it is loudest on the offside of the car) that is louder on accelerating, not sure if this is related. This video of me testing the DPF differential pressure signal wire contains the sound of the engine on idle and while it is revving on idle (https://drive.google.com/file/d/1SfIBwlzODhr4Rjy9tdwqpNCoTVE_anyY/view?usp=drive_link). What are your thoughts as to what could be causing these issues? Any help would be much appreciated!

If it starts, it'll start all day long, if it doesn't it fires up for a second or two, dies and then if the battery lasts long enough I have to crank it and crank it, eventually firing on one then two then runs, it's like it starts on the fuel remaining in the high pressure pump /rail then runs out of fuel until eventually more arrives, it's been suggested the lift pump in the tank may have failed but there are no warning lights on, no codes stored and once it starts it runs fine all day, generally it'll start if it's been run in the past 24 hours or so but leave it a couple of days and it's a pig. So far, service including fuel filter, new battery. any suggestions would be appreciated, oh and idle isn't smooth and occasionally I get the dumper truck idle when it's been run and idling for a while. other than driving me insane it's a lovely car, Audi A4 B7 2007 2.0 TDi S-Line Cabriolet