Low TJ oil pressure = new oil pump?

The oil pressure gauge on my TJ is high, 40+, while the engine runs at
road speeds, but at idle the needle sometimes drops to zero, and then
climbs up to about 10 pounds. Sometimes while at idle it swings back
and forth between 0 and 10.

I disconnected the electric oil pressure sending unit and attached a
mechanical gauge... same behavior... the pressure falls and rises at
idle like before.

The Jeep is a 1997 TJ 4 cylinder, with 71,000 miles.

Apparently I need a new oil pump. But I wonder if the oil pump might be
good and something else is causing the deviance.

Is the pump driven by the distributer shaft?... could the pump be good
and something else is causing the oil pressure to sometimes drop and
rise like that?

The Jeep runs well and behaves normally at idle or road speeds.

I change oil and filter every 3,000 miles.

TIA for your advice.

Ralph


God exists, or God does not exist, or I am God and I am dreaming all
this.