As far as I know both your Rangie and mine use the Lucas derivative of
the Bosch L-Jetronic design whereby there is either an air flow sensor
(flapper) or air mass sensor (hot wire) that indicates to the computer
the amount of air entering the engine so the fuel injector volumes can
be adjusted accordingly. Any air not entering the engine through this
meter disrupts the performance. Most engines with this system even go
so far as to have o-rings on the dipstick to avoid air leaks. Many
times it will kill and idling engine to just disconnect a vacuum line
or crankcase ventilation line. I think this book
http://www.amazon.com/exec/obidos/ASIN/0837603005/qid%3D979964569/103-2818012-3446229
is the definitive volume on these systems and it states "a loose oil
filler cap or dipstick can lean the mixture by admitting extra air to
the intake manifold through the PCV valve." I searched my copy for
tips regarding general engine condition and didn't find much, but it
seems likely excessive crankcase blowby would be problematic, if for
no other reason than this air is not particularly pure and could
affect "mixture" quality. Feels like it's more difficult, if not
impossible, to compensate for anything but minor engine wear on newer
EFI engines as compared to the old carburetored variety. I call it
the "Bob Dylan" syndrome: A carb knows what your engine wants, but EFI
knows what it needs.
The Becketts wrote:
> Kent,
>
> Grateful if you'd explain the significance of this? My EFI Range Rover has
> a very high crankcase pressure (blowby) which is causing seals to leak. I
> was thinking of just removing the hose between the rocker cover and plenum
> chamber to let the crankcase breath a bit better , i.e., to relieve the
> crankcase pressure.
>
> I'd need some sort of breathing oil cap on the rocker cover, perhaps from a
> Sixties car (pre-emissions).
>
> Ron Beckett
[This message delayed, as it needed manual intervention by the list
administrator. mjb.]
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