Evening,

Looking for a bit of advice on a 2003 Golf GT TDI PD130 (ASZ Engine) which I have owned for the last month or so.

Faults/Symptoms:

Low mpg (Was getting 45mpg on my daily work journey, now varies between 30-35mpg)
Intermittent rough idle/judder on tickover. (Not present when purchased, appears to have started at the same time as low mpg)
Smokey Cold Start (Only when left overnight & smells of diesel, possibly over fueling? Was present day after purchase............. it was warm when I bought it!)

Work done since purchased:

Oil & Filter Change
Fuel Filter
Air Filter
Pollen Filter
Brake Pads & Disks, front & Rear
Coolant temperature sensor changed (Hoping to solve cold start problem)
Coolant flush & new G12 added

After a bit of reading yesterday I now realise that there is also a thermostat sensor on the cooling system that it would have been sensible to change at the same time as the coolant flush, however at the time I was confident that it was not at fault as the dash readout was constantly sitting at 90 degrees once the engine had warmed up as expected. I decided to log the temp readings in VCDS on my journey to work this morning which gave me the following:

Temp Graph.jpg

It appears the engine is only hitting 68 degrees rather than the expected 90 which i assuming is the cause of the low mpg.

So my question is could this also be the cause of the intermittent rough idle/judder & the smokey start? I have read various posts regarding smokey starts and it seems to be a common problem? A simple fix with a thermostat would be great! Also what are peoples thoughts on the Intake air temp on the graph above? The temperature was 6 degrees when logged it this morning. Should i be looking to change the air intake sensor too, could that be adding to the symptoms?

Sorry for the long post just wanted to get as much info out there as i could.

If there is anything else I could log in VCDS to help diagnose just let me know what blocks to read if you could. Been using it for a while to read codes, just trying to get my head round its full capabilities

Thanks
Dan
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