4jx1 oil pressure problems

[phones]

Help! I have a 98 3.0 4jx1 Bighorn with low oil pressure issues. I had noticed that the oil light comes on after the engine has been running for maybe 10mins or so, and there is a major loss of power, almost to the point of thinking no turbo! the oil light only comes on when the engine is at idle, say waiting at the lights or in auckland traffic jams. Any increae in revs kicks the light off. My local mechanic has done an oil change new filters, oil pressure switch with no change. an external guage shows excellent pressure when first started from cold, but it then drops to bugger all after a few mins. Any one seen this before or know of a cure or at least where we need to look next. Your help is greatly appreciated.

[mtironauto]

Hi there, in the sump there is an o-ring on the oil pick up which is above the oil level. this sucks in air and can cause the oil pressure to drop. sadly it is the engine and gearbox out to fix it. try overfilling the oil by a litre or so to raise the level past the o- ring so it cant suck air. if that fixes it then i guess leave it overfilled a bit. good luck