I’ve got a 1994 Honda with a VTEC SOHC engine. My daughter, while away at college, drowned this vehicle in the aftermath of hurricane Henriette, in Amarillo, TX. It now runs, but with a problem I can?t solve. It had no oil pressure. I placed a manual pressure gauge in it and confirmed what the light was indicating. I replaced the oil pump, cleaned the oil pick up tube and went back with fresh oil and filter. It runs superbly, the engine has good pressure, indicated by the new in car gauge, except if I pass a car, (or stomp on it) the engine will gradually lose all oil pressure. If I stop and kill the engine, the moment I turn it back on, it pressures up again. I can drive for a short bit and it will lose pressure again. If I turn it off and wait 3-5 seconds it will pressure up again. What gives?
It sounds like something is getting sucked into the pump inlet when flow is high and falling out when you shut it off. The trouble with that analysis is that you had that all taken apart.
Just a wild guess here (a real wild one) but could it be possible that oil drain holes in the engine block and cylinder head are clogged or sludged up?
After running for a few minutes oil is being pumped upwards much faster than it is draining back down.
This means the valve train area underneath the valve cover would have heavily pooled oil and the oil pan, while maybe not being totally empty, may be low enough that the pickup tube can’t siphon any oil?
I suppose this could be verified by running it stationary with elevated RPMS. It’s assumed by me (right or wrong) that this problem should exist while the car is sitting. Once the pressure drops, remove the filler cap and note if oil is piling up inside the valve cover.
Just a thought anyway since the oil pump has been replaced and the pan/pickup tube has been cleaned.
just a thought. do you do your own oil changes? if so, use a clean bucket this weekend and do an oil change. measure the oil after you have gotten it all out. are you getting the normal amount out? doe sit keep draining long after it should be empty? put new oil in, and use a lighter weight oil. run the car for a day or two, then do another oil change. measure the oil. still getting the sam eamount out? and is the oil really dirty after just one day of use? i would suspect the clogged drains in the rocker arm valve cover area is a really good place to look. try running the engine and revving it up for a while. when the oil pressure drops, look in the oil fill cap. although i dont know your engine, most cars have a visible rocker arm or two to see if there is a whole lot of oiil up there when running.