low oil pressure at idle

[slam22]

my 1995 m3 has been triggering the low oil pressure switch after the engine is well warmed up and only at idle. The engine has only 43K miles with a low boost powerdyne supercharger installed at 18K miles. It is not the factory pressure switch but a VDO barrel type switch with two leads on top, one for oil pressure guage, the other for factory idiot light. When I removed switch and put a guage directly in port I got 10psi warm at idle jumping instantly to 60psi with elevated engine speeds. I am assuming the switch is preset to 7psi. Bad oil pump...crank bearings??? any help would be appreciated.

[E36M34life]

The only way I can help you is to wish you luck.......... GOOD LUCK!

[Balthazarr]

Restrictive oil filter?

[thejlevie]

The direct pressure measurement tends to say that you don't have a pressure problem. 10psi at idle on a hot engine is ok. That suggests that the VDO sensor might be bad. But as Balthazarr pointed out the oil filter could be reducing your idle pressure. Try swapping in a new BMW filter.

What oil are you running? BMW 5w30 synth is a special blend that runs a bit more viscous than a generic 5w30. The German 5w30 Castrol or Mobil 1 0w40 are equivalent to teh BMW stuff.

[mproved]

Bad oil pressure switch. I had a similar problem. My idiot light would go on after reaching operating temp, but my VDO gauage said I was at 10psi. I just ordered a new oil pressure switch from BMP Design and solved my problems.

[vinnymac]

10PSI at hot idle seems fine to me. You probably have a bad oil pressure sensor.