1987 4runner DLX, 22RE, AT, ....recent head replacement on a remann 2014 engine long block. Got 66K, 7.5 years and headgasket went. Mechanic stated cost of warped head about same as new remann head with cam. Did that and replaced oil pump, h2o pump, chain, etc. Valves relashed after about 500 miles, oil change 10W30 Quaker conventional.
Anything to increase OP?
Idiot gauge on dash reads about 1/4 to 1/3 during operation and not much of anything at idle (1K).
What can be causing this? Originally it always had about 1/2 OP showing....Thanks

 

The gauge or sensor getting old/dirty. The sensor getting corrosion on the threads, or some corrosion in a connector between the sensor and gauge. Loose screw, or dirty connection on the circuit board it's mounted on.

Different oil pump, different setting of the bypass valve. Leaky seal around the oil pump.

Almost nothing at idle is actually about the right reading, and 1/3 to 1/2 is normal at 2500 or above. Those gauges ARE notoriously inaccurate, but almost nothing is the correct idle reading.

Hope this some help...
Pat☺

 

My $0.02: Unless you have an accurate indication of engine oil pressure, you don't know whether it's too low, just right or higher than necessary. My other automotive interest is Chevelles. The Chevy performance gurus seem to agree that 10psi per 1,000 rpm is fine for a performance Chevy V-8. Should be OK for a plain vanilla Toyota 22RE. I had to go out and look at my '89 pickup to see if it has an oil pressure indicator. It doesn't, just a red warning light if pressure is insufficient. Not for me to question Toyota designers/engineers. Until you have an accurate indication, you can't know if you have a problem. First trouble-shoot is to ensure good solid electrical connections and grounding.

If I would be worried about a situation like you have posted, I'd arrange a mechanical indicator something like:

https://www.jegs.com/i/Sunpro/885/FS...r%20Categories

You would need a suitable adapter to metric threads for the connection to an oil gallery. Mechanical indicators have a 270" sweep on the scale. Electrical would be OK. I prefer mechanical myself.

 

Making sure connections are clean and tight is good.
Even brand new this concern often came up with customers, even on other models like the Supra.
At idle the minimum spec is 4.3 psi. at 3,000 rpms it's 35-36psi.
The gauge doesn't have a numbers, but essentially, if the needle moves at all at idle it should be fine, and anything close to 1/4 or higher while driving should meet the requirement.