Hi Guys
Not a regular poster on here but have been monitoring this thread and others describing similar symptoms with interest having encountered almost identical behavior with my 1998 PF S8.
Problems began around 2 years ago during a signature British summer-time downpour, whilst moving in moderate traffic the car felt sluggish and laboured. At first blaming a new pair of thick-soled shoes denying me the usually tactile feel of the cable actuated throttle, panic truly set in having driven through a large puddle on the nearside of the carriageway illuminating the ABS, ESP and CAT warning lights as well as the dreaded PRND234 in inverse lettering.
Restarting the car at the side of the road cleared the warning lights but performance remained hesitant and unresponsive.
Directly arriving home I read off the 3 reported faults (16505 Throttle valve potentiometer G69 - Implausible signal, 18265 Load signal - fault message from engine control unit, 17087 / P0703 Brake light switch - intermittent)
The trend was set from this point, every time it rained I could expect problems at least for the first mile or so. At first suspecting a problem with moisture/tracking the theory was disproved when exactly the same behavior occurred whilst overtaking a bus on a perfectly dry day.
Having initially tested and adjusted the existing unit according to Elsawin, I decided to replace the throttle position sensor on a whim and repeat the alignment procedure. Checked the ever expendable crankcase breather hoses which although soft, appeared to be intact. The next port of call was the bulkhead box housing the various control modules on the nearside of the car which appeared to have received almost tidal punishment from the outside was found to be clean and dry inside. Dressed the electrical contacts with contact cleaner, left it to dry then re-assembled with some gasket sealer around the now weathered rubber seal. Set the engine running and had 20 minutes with a can of easy start attempting to identify any air leaks which may have developed (none were found). Any impression of improvement may have been wishful thinking as the problem persisted on some occasions yet not on others.
The real breakthrough then occurred by accident. Having religiously filled up with BP "Super "plus" 97RON under the delusion that the product offered slightly better fuel economy, the local filling station only had regular unleaded available on this day. Having continued to use this grade of fuel for a month or two I have yet to encounter the hesitation to anything like the same degree as before however I cannot say for definite that these actions have cured the problem or simply masked the symptoms. Have others had any success using different fuel/suppliers? Now I come to think of it, the problems began shortly after moving house, before which I had always used Shell products. Coincidence no doubt!
Without drifting off topic too much does anyone know if filling stations have a separate storage tank for their "premium" fuels or is the product sold as regular unleaded with an additive delivered at the pump?
Mike
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