Oil pressure good at startup, after driving 10 or 15 min it gose down and out when stop. but will go up when givin gas. dose not knock or tap. its 86 ford bronco 302

oil pressure relief valve is a good place to start and of course oil level/condition plus oil filter for blockage

Are you hearing a knocking coming from the engine if so yeah there may be a rod getting ready to go soon which would be an engine replacement. Have you checked the oil levels? It could also be an oil pump or oil pressure sensor. There are many things to consider and many things it could be.

No if the oil light has flickered you have oil pressure loss some time just belive the sensor do help us out. lifter do not cause oil pressure loss pressure is built in the rotation of the crankshaft. The knock under the plenum will point you to that cylinder that is affected, (main bearing) as for a 1995 the injectors can only cause a misfire but no knocking noise,will they honor the warranty

Hello,
It sounds like your oil sending unit is not functioning. When this goes out you lose oil pressure. When the oil pressure drops the oil does not circulate and then your engine does not lubricate and will seize up on you. That's the knocking you are hearing.The oil light is on because of the drop of oil pressure. I would stop driving that vehicle until that oil sending unit is repaired. If you do not repair this at home or where the vehicle is at the you will want to have it towed to the point of repair. You can test the oil sending unit with a pressure gauge beforehand too but it sounds to me like it is bad. Sometimes they are easy enough to switch out. If you give me your make and model and year of vehicle I can list the steps and location for you. Other wise have it towed to a mechanic. I would like to reiterate that you should not drive it anymore until it is repaired. The other thing that it could be is your oil pump. Either way stop driving it.
Regards, Tony

Check fuel pressure first when the car stalls or dose not start. If you get no fuel pressure check if you get any power to the fuel pump if you do replace the fuel pump with stariner and fuel filter to prolong the life of the new pump.

the cure depends upon the problem: Knocking is usually down low and is generally an engine bearing problem. If you hear a tapping noise (lighter than a knock) and oil pressure is good it can be caused by wear of the pivot for a rocker arm, a worn lifter or lifter and camshaft or a broken valve spring. Tapping can also be caused by low oil pressure in which case it can be due to low oil level, obstructed pump pickup or worn engine bearings. If you are unfamiliar with any engine repair, get a chilton or haynes manual to guide you through whatever needs doing.

a knock from the bottom of the motor is a big end bearing STOP DRIVING, new engine or rebuild required, a knock from the rear of the engine could be loose pressure plate on clutch assembly, that is if it is a manual, STOP DRIVING. a rattle from top end is lifters or rockers but you say its a knock so probably not it. one test to do, remove all drive belts to water pump etc and start if the knocking is still apparent then it is internal and time to consider trade in, rebuild or new engine.

are you using the right octang of gas.

Most likely ignition switch has gone bad.  Don't need to worry about oil pressure light IF the motor is not running, but IF it IS running, shut down motor immediately until oil pressure can be verified with an external gauge.
good luck

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