Questions and Answers
Mustang Loses Oil Pressure
Q. I have a 1992 Mustang (four cylinder 2.3 liter, auto, FI, P/S, A/C, CC, with 90,000 miles). The dip stick shows the oil level on full. It has been about 400 miles since the last oil change. The oil has been changed regularly at 5,000 mile intervals since new.
When the engine is cold the oil pressure reading is normal. After driving 10 miles at 65 mph the oil pressure suddenly starts rapidly heading south. Slowing to 55 mph restores the normal oil pressure reading for a few minutes and then it again heads south. Slowing to 40 mph restores the normal oil pressure reading (more or less).
Stopping the car (engine is now warm) and shifting into neutral results in a normal oil pressure reading from idle rpm through 3,000 rpm.
Stepping on the brake, shifting into reverse results in a normal oil pressure reading at idle rpm, but the oil pressure immediately drops with any significant increase in engine rpm.
In summary, once the engine is warm, the oil pressure will head south anytime the engine is asked to pull a load at any speed much above idle.
I would suspect a faulty oil pressure switch/gauge if the oil pressure were to either randomly jump around or to simply to tend to remain in one place most, if not all the time.
Is there anything that could be sticking or plugged up that can be fixed by something other than pulling the oil pump?
Thank you,
DavidA. The first thing to do would be to hook up a mechanical oil pressure gauge to confirm the gauge readings. If the mechanical gauge shows normal operation, then the Oil Pressure Switch (OPS) is faulty. If the mechanical gauge confirms the readings, then I would suspect the spring in the oil pressure relief valve is weak or broken.
The 2.3 liter engine in your car is not a real high quality engine. As they get older the bearings get worn and allows oil to "leak" out resulting in lower oil pressure. I don't know what weight oil you are using, but a 10W-30 might help. If you live in a climate that is warm year round you might try a straight 30 weight. This is assuming there is no mechanical problem with the oil pump.
Additional Information provided courtesy of ALLDATA
