Ertdes
New Member
Hi everyone,
Background
I have an AUDI A3 1.6 TDI 2010 (8PA), 126K mileage. Last year, it was overheating and so was driven without a thermostat for approx. 6 months until the cause was identified and fixed (it was the heater matrix which was replaced alongside the heater matrix connecting pipes). In hindsight, this wasn't the best idea for the car's DPF but circumstances at the time forced me to. The car had its MAF sensor changed last month; the thermostat, water pump, electric water pump, timing belt and auxiliary belt were changed last year.
Issue - Intermittent High Idle
Having driven this car for several years, normally its RPM on idle is 800 and before last year I had never seen it increase beyond that on idle (I primarily did motorway driving).
Whilst driving the car without the thermostat last year, the car intermittently initiated active DPF regeneration which I could tell by the RPM on idle increasing to 1000 with an associated increase in engine temp. to 90deg C and stopping of start-stop. Once the heater matrix was replaced, the car would continue to have intermittent periods of a high idle at 1000 RPM but on the most part it would be 800 RPM (this was despite me doing some motorway driving at least fortnightly).
For the past week, the car seems to randomly switch between 800 RPM idle and 1000 RPM idle. There is also an added sound from the engine bay that is louder when accelerating. Yesterday, it was idling at 1000 RPM so I took it for a drive on the motorway in case the DPF was actively regenerating but turns out it was not and the RPM decreased back to 800 once I reached home.
Just today when driving to work, the engine RPM remained at 1000 during idle, with 3 'blips' of the idle RPM reducing to 800 but then suddenly increasing back to 1000. When driving back from work, the engine RPM was 800 and then I heard a grumbling sound from the engine bay, after which the RPM increased to 1000. Turns out the car had actually started a DPF regen this time so I took it out for a motorway drive again and upon returning home the RPM reduced back to 800.
Having done some research, I am suspecting one of the following:
- Bad DPF differential pressure sensor
- Blocked DPF
- Bad alternator
- Weak battery (the car does take longer to start on some occasions)
What could be causing this issue?
There were fault codes relating to central electrics (not sure if this is related, the car sometimes displays a central brake light warning when pressing the brake pedal but the brake light is working) but otherwise nothing else. Here are the links to the videos of my OBD scanner live data and to the voltage changes in the signal wire from the differential pressure sensor when revving the car on idle (sorry for the scanner beeping!):
Apologies for the lengthy read; I'm new to cars so wanted to give the details in case they are important. I'd rather avoid another fiasco like the one with the heater matrix last year so any help would be much appreciated! Thanks in advance!
Background
I have an AUDI A3 1.6 TDI 2010 (8PA), 126K mileage. Last year, it was overheating and so was driven without a thermostat for approx. 6 months until the cause was identified and fixed (it was the heater matrix which was replaced alongside the heater matrix connecting pipes). In hindsight, this wasn't the best idea for the car's DPF but circumstances at the time forced me to. The car had its MAF sensor changed last month; the thermostat, water pump, electric water pump, timing belt and auxiliary belt were changed last year.
Issue - Intermittent High Idle
Having driven this car for several years, normally its RPM on idle is 800 and before last year I had never seen it increase beyond that on idle (I primarily did motorway driving).
Whilst driving the car without the thermostat last year, the car intermittently initiated active DPF regeneration which I could tell by the RPM on idle increasing to 1000 with an associated increase in engine temp. to 90deg C and stopping of start-stop. Once the heater matrix was replaced, the car would continue to have intermittent periods of a high idle at 1000 RPM but on the most part it would be 800 RPM (this was despite me doing some motorway driving at least fortnightly).
For the past week, the car seems to randomly switch between 800 RPM idle and 1000 RPM idle. There is also an added sound from the engine bay that is louder when accelerating. Yesterday, it was idling at 1000 RPM so I took it for a drive on the motorway in case the DPF was actively regenerating but turns out it was not and the RPM decreased back to 800 once I reached home.
Just today when driving to work, the engine RPM remained at 1000 during idle, with 3 'blips' of the idle RPM reducing to 800 but then suddenly increasing back to 1000. When driving back from work, the engine RPM was 800 and then I heard a grumbling sound from the engine bay, after which the RPM increased to 1000. Turns out the car had actually started a DPF regen this time so I took it out for a motorway drive again and upon returning home the RPM reduced back to 800.
Having done some research, I am suspecting one of the following:
- Bad DPF differential pressure sensor
- Blocked DPF
- Bad alternator
- Weak battery (the car does take longer to start on some occasions)
What could be causing this issue?
There were fault codes relating to central electrics (not sure if this is related, the car sometimes displays a central brake light warning when pressing the brake pedal but the brake light is working) but otherwise nothing else. Here are the links to the videos of my OBD scanner live data and to the voltage changes in the signal wire from the differential pressure sensor when revving the car on idle (sorry for the scanner beeping!):
- Central Electrics Fault Codes -
View: https://drive.google.com/file/d/1CYhup8KtI_soYIT3GZccJlB0DOkrzQDG/view?usp=drive_link - DPF Differential Pressure Sensor Data When Revving on Idle -
View: https://drive.google.com/file/d/1RRqb7kV-127tNKCKAXcZzYAZhcQop9Fc/view?usp=drive_link - DPF Differential Pressure Signal Voltage -
View: https://drive.google.com/file/d/1SfIBwlzODhr4Rjy9tdwqpNCoTVE_anyY/view?usp=drive_link - Live Data Before Startup -
View: https://drive.google.com/file/d/1mrM2FYaRHj6F0vprtA2wcSH3reyDvQ7C/view?usp=drive_link - Live Data After Startup -
View: https://drive.google.com/file/d/1GKbyMvDhbS7m14or7kdpaxpPWLUgvemr/view?usp=drive_link - Live Data Showing High Idle -
View: https://drive.google.com/file/d/1bzlM-xskRXvUuxdzOGXumVwP7iUbMul3/view?usp=drive_link - Live Data After Motorway Driving and DPF Regeneration -
View: https://drive.google.com/file/d/1f1MBNR8ly8T09OhCyPOtYH-W22ZW7B7m/view?usp=drive_link
Apologies for the lengthy read; I'm new to cars so wanted to give the details in case they are important. I'd rather avoid another fiasco like the one with the heater matrix last year so any help would be much appreciated! Thanks in advance!
