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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21093
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an 2005 Audi A8 W12 6 litre. The... I have an 2005

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I have an 2005 Audi A8 W12 6 litre. The...
I have an 2005 Audi A8 W12 6 litre. The fault code reader is telling me that I have an Camshaft Sensor fault P0346 camshaft position sensor A Bank 2 OKT Range/Perf, along with P0348 Camshaft position Sensor A - Bank2 circuit High input. I also have a 18341 Throttle actuator 2 Malfunction P1933sporadic 008 implausible.
I had to change the battery this week, as it ran flat. The recovery guy notice a fluctuating draw on the circuit from 0.3 amps to 0.8 and back again, despite all electrics turned off.
The car runs, and is driveable, but the engine at static doesn't feel like its revving properly, and out on the road, if you hit the throttle, it sounds almost like a blowing exhaust - but having had it checked out, numerous times there's no evidence of this.The camshaft sensors are incredibly tight against the bulkhead, so what is the procedure to replace a defective unit?RegardsJon
Submitted: 8 months ago.
Category: Audi
Expert:  Matt replied 8 months ago.

Hello

sorry to say that like most things with the W12 unit then the engine has to be partially removed / dropped on its mounts to gain enough access to replace the cam sensors

a faulty cam sensor will prevent the variable cams from functioning correctly and they will remain locked in the 'safe' starting position - this results in a lack of performance and loud exhaust - as you have already noticed

if the 2nd throttle is also giving issues then it may not be opening fully either

this parrt at least is easy to access and you cna check it over by removing the air intake pipe and then with the ignition on and engine off, have your assistant slowly push down on the accelerator whilst you watch the throttle move

it should move steadily and smoothly with no jerkiness - if you spot this then 1s ttry cleaning the throttle and if that doesn't help then replace the throttle body

Customer: replied 8 months ago.
Ive checked both throttle bodies and cleaned them, had the reset with the VAGCOM . All working fine, so unsure what is causing the code there. Perhaps tied in to the Sensor problem?
As far as dropping the engine, is that a case of supporting the engine and removing the hyrdraulic mounts, or is it a ramp job where engine and and box have to be lowered as one unit from below.
Also, if I removed the head on one side, would this get where I need to be?
My problem is that to take it to Audi, would be off the clock cash wise. The car is worth £7k and I would like to move it on, so I'm reluctant to lay out thousands in having the engine dropped. I'm a competent mechanic myself, but I,m just shocked at how ridiculous the engine bay is to work on.
I'm also wondering if the cam sensor is merely a bad connection rather than a fault? As there is very little in a cam sensor to go wrong.ThanksJon
Expert:  Matt replied 8 months ago.

Hello

I'd also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

and it would also be worth measuring the fuel pressure at the injector rail with a running engine as this will show if the main engine pump is in good condition

as low pressure will limit power and engine rpm

Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21093
Experience: BEng hons Mech engineering, in auto industry 22 years
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