I just purchased 97 4Runner with 3.4l engine. Several times during my 800 miles trip low oil pressure light came on right after I stopped at idle. At about 700 rpm it was on and was off when rpm went above that. I checked oil level several times during the trip and it was full and engine does not appear to burn any oil. I was driving it before on short trips and had no light coming on. I just have a light for oil pressure monitoring and no gauge. I was wondering what is the best way to deal with it. Should I install new sensor and observe behavior or should I get a gauge and sending unit? Thank you for all your help.

 

change the oil in it and put a new oil filter on. Maybe use a higher weight like 10W40 or 15W40 (diesel oil) and then go from there. A real gauge is a good idea, but that idiot light comes on at a very low pressure. Is the engine making any knocking sounds when the light comes on, Not that it is but sometimes low oil pressure like that can be a sign of a bearing failure somewhere as well.
If changing the oil and filter doesn't help then look into the pressure sender.

BTW it is perfectly normal for the oil pressure to fluctuate from idle to driving rpm but should never trip the oil light at idle.

 

Change yer filter ASAP... My cousin's did that, though in a POS Chevy, the cause was the filter collapsed inside...

 

Just remembered I have not updated my thread and in case someone else have the same problem they can see what works best. Before I'll start tearing the engine apart I have decided to install oil pressure gauge instead of changing sending unit. I followed instructions from here: http://www.4runners.org/writeups/gaugeoil/index.html
The only thing I would add that I have installed 4A fast acting fuse as recommended by Autometer. Now I have exact numbers to go by. At cold start I get 80 psi, at idle once it's warmed up it's 15 psi.
I also found interesting thread: https://www.yotatech.com/forums/f2/o...licker-131175/
The official Toyota 1998 4runner Owners Manual, Chapter 1-5 p.69:

"(d) Low Oil Pressure Warning Light

This light warns that the engine oil pressure is too low. If it flickers or stays on while you are driving, pull off the road to a safe place and stop the engine immediately. Call a Toyota dealer or qualified repair shop for assistance.

The light may occasionally flicker when the engine is idling or it may come on briefly after a hard stop. There is no cause for concern if it then goes out when the engine is accelerated slightly.

The light may come on when the oil level is extremely low. It is not designed to indicate low oil level, and the oil level must be checked using the level dipstick."