Odd oil pressure problem in '89 Spider
My "89 Spider (87k miles) is in pretty good shape, uses maybe a quart of oil every 1000 miles, starts and runs well. Up until about two months ago, when started, the oil pressure would register 57 psi almost immediately and would drop hardly at all when idling. Likewise, the temperature always warmed to a rock steady 175, no matter what.
Then about two months ago, I made a mistake I've never made before in my life: I didn't replace the oil-filler cap after adding a quart of oil.
I drove the car for about 20 miles before the dropping oil-pressure caught my attention. Opening the hood, I saw that the cam chain had slung oil out the filler hole and all over the place under the hood. I'd lost about 1.5 quarts of oil. Obviously very uncool, but for a car with a seven-quart capacity, not fatal.
So I filled it up with oil, replaced the cap (which was still resting between the cam covers), and figured no harm had been done.
But now, when I start the car, the oil pressure remains close to 0 until I rev it a few times (i never had to rev it before). Once warmed up and going down the highway, the pressure will get up to about 50. But if I stop at an intersection, the pressure will drop to zero.
The engine isn't using any oil and when I look at the dipstick, the oil looks very clean. Everything seems properly in place.
Also, perhaps coincidentally, the temperature now runs a bit hotter (180-185), but not dramatically so. Still, it is a change from the absolutely rock-steady 175 I had before.
Any ideas? Could some oil passageway in the engine be blocked? Could my gauges be lying to me (even though the tach and speedo seem to be fine)?