'85 LG4 305
Completely stock internals
165,000 miles

Today when I was heading to school, I started the car up normally and it seemed fine. It was a bit cool out, but nothing extremely harsh.

After about a minute of warming up the car (which was idling at about 1500), I noticed that the car suddenly lost about 700 RPMs according to the gauge in the car and it started running really rough, all without me doing anything... just randomly started doing that. At first, I didn't really pay any attention to it and proceeded to head off to school. I got about half-way down my road and I noticed the engine sounded way louder than it should be, and it was struggling to rev at all when I pressed the pedal.

So I look down at all my gauges to see if something was up, and sure enough when my eye hit the oil pressure gauge, it was reading below the 10 mark on the gauge and not moving from that spot even when I pressed the pedal. I quickly decide to turn around and park the car in my driveway and shut it off. I take a look at the oil dipstick after a few minutes and it seems like it has plenty of oil, and nothing under the car appears to be leaking.

What could this mean? I know I shouldn't rely on the stock guage to tell me oil pressure due to it being inaccurate, but I know for sure that it at least worked before this happened and the car started running horribly out of nowhere.

I'm using Mobil 1 5W-30 synthetic.

 

It doesn't sound real good for the home team.

I'd quit running the motor, RIGHT NOW. Pull the distributor, and turn the oil pump drive shaft with a big screwdriver or something. Look at the dist and make sure it's OK where it mates to the drive rod.

If the dist is OK, and/or the oil pump drive rod doesn't seem right, about all that's left to do is drop the oil pan and see what's going on.

 

Thanks for the info.

Turns out I goofed real bad... I didn't tighten the distributor hold down bolt all the way and (I'm assuming) through normal engine vibration the distributor managed to wiggle its way up out of place and was not connecting with the oil pump drive shaft. I pulled the distributor and reinstalled it fully seated and oil pressure went right back to normal, and the roughness of the engine disappeared. I changed the oil to Mobil 1 10W-30 while I was at it, since I was planning to do it anyway.