V6 TDI Slow Idle - thoughts?
Discussion
Specifically this refers to a VW Touareg v6 TDI 2009 with 49k.
Over the last couple of weeks I've noticed that the car idle speed is lower than normal when cold. After the initial start, it would settle around the 800rpm mark and be quite smooth, but its started to settle around the 700 rpm mark and there is a small amount of vibration. A light touch on the pedal to take it to around 750 and the vibration goes.
Once the coolant and oil temps are up to normal, the idle is back to c800.
Aside from that, there is no issue starting the car, no loss of power when cold and it drives and accelerates as normal at all temperatures.
Even when idling at 700, it is even and steady and the engine sounds fine, the only real clue that something isn't right is the very slight vibration and the fact I know that 700rpm is lower than it normal is.
There is no smoke from exhaust, oil level is fine and coolant level is fine.
I've plugged in the code reader and no codes thrown at all. The slow idle fluctuates between 680 and 682, so very steady but probably c70 extra RPM stops the slight vibration. Once warmed up and idling in its normal manner, its reading 780rpm
I'm going to get hold of some Forte \injector cleaner, but what other thoughts do you have?
Over the last couple of weeks I've noticed that the car idle speed is lower than normal when cold. After the initial start, it would settle around the 800rpm mark and be quite smooth, but its started to settle around the 700 rpm mark and there is a small amount of vibration. A light touch on the pedal to take it to around 750 and the vibration goes.
Once the coolant and oil temps are up to normal, the idle is back to c800.
Aside from that, there is no issue starting the car, no loss of power when cold and it drives and accelerates as normal at all temperatures.
Even when idling at 700, it is even and steady and the engine sounds fine, the only real clue that something isn't right is the very slight vibration and the fact I know that 700rpm is lower than it normal is.
There is no smoke from exhaust, oil level is fine and coolant level is fine.
I've plugged in the code reader and no codes thrown at all. The slow idle fluctuates between 680 and 682, so very steady but probably c70 extra RPM stops the slight vibration. Once warmed up and idling in its normal manner, its reading 780rpm
I'm going to get hold of some Forte \injector cleaner, but what other thoughts do you have?
Get it code read with a decent reader, not all issues will flag up an MIL you really need to read the live data and compair the sensor range with manufacturer specs ect, it could be an ECU temp sensor going down or the throttle housing may need a clean, de sooting the inlet possably? lack of air flow due to blocked inlet manifolds is a prime issue on modern diesels, i buy Mr muscle by the case i do so many inlet tract cleanouts 
I think I've solved it - there was a leak where the air inlet and turbo connect - some return gases were escaping and cooling - the mating surface was filthy - cleaned up and a good steady idle is back. Must have been air/fuel ratio until the turbo housing got hot and expanded to seal any gaps.
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