Audi TT 180 Quatro Roadster White Smoke

Hello all

Help needed with this one.

The car is a 2000 Quatro Roadster 180 and it had an annoying issue where the engine temp wouldnt get to 90'c and the car was doing real bad MPG.

So this weekend I replaced both the thermostat and the temp sensor, and whilste I was going to drain the coolant I thought it wise to flush the engine and replace.

The coolant in the expansion tank was orange and with some sediment in the bottom, this was the main driver for changing and flushing the system as I belive that the blue anti freeze has been mixed with the pink.

Replacing the parts wasnt too taxing, but done and no leaks present.

Prior to filling the coolant, I filled up with just De-Ionised water, purchased from Halfords and then ran the engine for 10 minutes, let it cool down, dropped that coolant then topped up with the G12 Antifreeze and de-ionised water and let the engine run.

Now here is where the problems start.

Now when first starting the engine, the revs drop to around 600rpm, then idle back up to around 900rpm after that they are ok.

When reving the engine at around 3,000rpm, it produces white smoke, not steam but smoke it also smells of fuel.

Took the car out for a test drive, the temp was back at 90'c and the 49'c trick showed the figure of 83'c and 51'c at 90'c.

And on the way back the CEL came on and I did a quick scan with Vag-Com and got the following codes:

VAG-COM Version: Release 409.1-S

Chassis Type: 8N - Audi TT
Scan: 01,02,03,08,15,17,22,35,37,45,54,55,56

-------------------------------------------------------------------------------
Address 01: Engine
Controller: 8L0 906 018 Q
Component: 1.8L R4/5VT 0002
Coding: 10710
Shop #: WSC 01236
TRUZZZ8NZ11027875 AUZ5Z0YD130027
5 Faults Found:
17526 - Oxygen (Lambda) Sensor Heating: B1 S2: Open Circuit
P1118 - 35-10 - - - Intermittent
17522 - Oxygen (Lambda) Sensor: B1 S2: Internal Resistance too High
P1114 - 35-00 - -
17704 - Error in Mapped Cooling System (usually temp Sensor or Thermostat)
P1296 - 35-10 - - - Intermittent
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
17840 - Secondary Air Injection Solenoid Valve (N112): Open Circuit
P1432 - 35-00 - -
Readiness: 0000 0000

The Mrs said that the car was smoking again from starting this morning and create a small cloud before she set off....


So my questions are;

1. Is this the headgasket that is now going, and has the flushing allowed the gasket to fail more. No visible oil in coalant, no white bits in the Oil.
2. Could the smoke be just because of the Lambda Sensor failing? Are they easy to replace?

If I search on this forum it generally points so head / headgasket cracked / failed. Or a faulty turbo... but it seems to be too much of a coincedence with changing the coolant.

Help needed or a decent VAG specialist in the Notts area would be of great use!!

Cheers

Stuart