Calum

Hi mate, a common failure on VAG cars, I just changed mine yesterday before it fails. If you look at the bulkhead behind the coolant reservoir there's three large electrical connectors. The grey one in the middle is for the crank angle sensor follow the wire and it will lead you to the sensor. It will be around the oil filter area and is held by one ten mm bolt, I changed mine when I had the oil filter off for better access. Here's a guide https://www.pelicanparts.com/techarticles/Audi_B6_A4/12-ENGINE-Crankshaft_Positioning_Sensor_Replacement/12-ENGINE-Crankshaft_Positioning_Sensor_Replacement.htm

Cheap enough on EBay https://www.ebay.co.uk/itm/Cam-Chain-Tensioner-Timing-Holding-Tool-For-VW-Audi-1-8T-2-7-2-7T-2-8-3-2-4-2-UK/152498732342?hash=item2381a1fd36:g:8JIAAOSwh1paD~Bi

The Audi won't run well with a dump valve as they're not designed to run with them. They have a diverter valve a more popular choice is to fit a Forge diverter valve such as this http://www.ebay.co.uk/itm/Forge-Motorsport-VAG-1-8T-Turbo-Recirculating-Dump-Diverter-Valve-FMDV008-Black-/112198035082?hash=item1a1f86268a:g:YRMAAOSwB09YDg~G

Use this oil, http://www.ebay.co.uk/itm/Quantum-Longlife-3-5W-30-Fully-Synthetic-Engine-Oil-5-Litre-Bottle-/131453080952?hash=item1e9b36d578:g:NSAAAOSweW5VAFXT And these plugs http://www.ebay.co.uk/itm/NGK33-Spark-Plug-x4-PFR6Q-Audi-Seat-Skoda-Volkswagon-BNIB-/131992293488?hash=item1ebb5a9070:g:Yw8AAOSwx2dYG2pe And this oil filter http://www.ebay.co.uk/itm/Mann-Oil-Filter-Spin-On-Type-Audi-A4-1-8-T-Quattro-Performance-Service-Engine-/231318345475?hash=item35dba5d703:g:aekAAOSwVFlT~mo5 I wouldn't use a flush, as long as you do regular oil changes circa 5000 miles it should be okay, does it have good service history and have you ever had LOW OIL PRESSURE warning? Hope this helps, I've had experience with 1.8t engines for over 10 years so any questions just ask.

Hi, I've just joined the forum, that bolt is a front subframe bolt and I'd be really worried that you're driving around with one missing.There are four of these and they are stretch bolts. Have you had any recent work done, ie sump removal?