On Friday, July 1, 2011 9:44:10 AM UTC+10, Bill Leary wrote:
> The car is a 1987 16 valve Scirocco.
>
> When the engine gets up to operating temperature, and it's run between 2200
> and 2800 RPM the oil pressure warning activates. Get it above 2800, it
> shuts up. If it falls below 2800, it activates again. Gun it, to get it
> above 2800, then shift so it's running below 2200, it stays off. Bring it
> up to 2200, and it activates again.
>
> Any ideas?
>

If the OP is low, you should be able to hear the bigend bearings hammering. It wont necessarily be that loud, but present all the same.
You warm the engine, then using a jerky motion, gun the throttle so it goes to about 2500 rpm. If they are crook, you'll hear a soft "brapatatatat" noise.

As to how this is happening? Its likely due to advanced wear of the BE shells and or the crank-journal is worn out of spec. There are other possibilities, like blocked oil-galleries due sludge, stuck pressure-relief valve, too thin an oil. Engines that have advanced wear *should not* be run with synthetic oil,..use mineral 20w-50 or 20w-60. Oil pump wear is not a common cause. But oil-pump pick-up gauze blocked due sludge, and a lackof oil-tight mounting of pump,..ie>>drilling may have the mounting bolts bottoming in their threaded holes [had a Valiant doing this]. Some3 times other bearings like the cam and or auxilary shaft bearings can rob the rest of the bearings of presure. Toss a new filter in her, in case its faulty...

Jason