Firstly, my fuel gauge started going non-linear such that I was recording 240 miles on the first half of the tank and only 140 on the second. Also, the low fuel light, which would normally come on with 8 litres in the tank, was coming on with only 3 litres
Clearly there was a problem with the fuel sender(s) but working out which one was going to be a challenge. In the end I replaced both which included a new fuel pump. Having delivered VPower for almost 19 years and 365k miles, it made sense as a bit of preventative maintenance.
All good now
The second issue was more challenging as I was experiencing a drop in engine note when running at steady state (say 70 on the motorway) with a resulting drop in power, sluggish throttle response and dreadful mpg. This was intermittent and somewhat random as to when it occurred and there were no warning lights. An ignition restart cleared it so it was liveable with.
Some code reading at the recent oil change revealed a problem with the inlet cam sensor - which makes sense as this would retard the Vanos, resulting in the subsequent symptoms. Removed the sensor and discovered the wiring into the sensor housing was fraying and I was getting occasional shorting out, triggering the fault and the protective response.
A new sensor later and all good
On a positive note, since the rebuild 18k miles ago, I am enjoying almost 4k miles per litre of oil
