I recently purchased a 1996 4cyl. with 132K miles on it. It seemed to run quietly and smoothly but as I was arriving home with the car after about a half hour drive the oil light started flickering as a stopped at a stop light. Bringing the rpms up evening slightly above an idle will cause the light to go off. There was evidence of oil leaking on the back side of the engine so I decided to replace the valve cover gasket. The inside of the cover badly caked with crud. I scraped and cleaned and got most of it but was/am concerned about the rest of the engine. I thought maybe the oil uptake screen could be clogged with same crud, causing the oil light problem so I dropped the pan. The screen and pan were reasonably clean. I have not removed and examined or replaced the oil pressure sensor yet. Any thoughts on why the light comes on at idle and what could be done to correct? And any recommendations for cleaning the inside of the engine? Thanks.

 

My suspicion would be a faltering oil sending unit or oil pump. Replacing the oil sending unit or pump would be a good first start. After the oil pump is replaced, I would recommend flushing out the motor with a safe engine flush, such as Amsoil engine flush. Refill the crankcase with petroleum oil, and inspect for leaks again. Drive the car, and if the oil light still flickers on, the problem could be with a loose wire or faulty oil pressure sensor.

 

Thanks for the response. Sinse the original post I replaced the oil pressure sensor with a dealer sensor and it did not fix the problem. There was a horrific build-up of crud under the valve cover. I have carefully scrapped and vacuumed out much of the build up from the top of the head and am replacing the valve cover as the build up all but totally filled the air space created by the plate riveted to the top inside of the valve cover. Following a recommendation I saw on another forum I ordered a couple of bottles of Auto RX to clean the engine as you suggest. I'll try to remember to give an update after the first cleaning.

 

I like the things you said you were doing. Question: I know you said you replaced the oil pressure sensor, but what about the oil pump? Did you change the oil pump? If your engine is dirty enough to warrant the cleaning that you've already done, think about how much gunk has been going through your oil pump...I would think it'd be easier to fill an oil pump with gunk than an entire motor, but that's just my opinion.

 

The gunk you refer to is engine sludge. VERY bad sign. Besides having the sludge in the head (from which you said you removed most of it - that is where it is created).... there is no doubt sludge in other parts of the engine. By the time it builds up to that degree in the head, it definitely will be in other places. You are doing the correct thing by performing an engine cleaning - actually, you should do it at least TWICE.

If the oil light comes on, it means that your oil pressure is below the threshold for the sensor, which is something like 3 - 5 psi. Oil pressure at idle should be 10 - 12 psi. The fact that the light is flickering probably indicates that the oil pressure is bouncing up and down at idle...between 3-5 psi and 10 - 12. This is a certainty, now that you've replaced the pressure sensor, with no effect. So, I'd agree that you need to replace your oil pump. They can fail without warning.....and if it fails while you are driving, you will likely destroy your engine (it can happen within 1 minute, with zero oil pressure). Most likely, there is sludge in the pump, or in the orifices near the pump.....and this is restricting oil flow at idle. The fact that the oil light goes out above idle speed is good....but you probably still have LOW oil pressure in the engine. DON'T take this lightly.

Doing the engine cleaning MIGHT restore the situation to normal....but that is iffy. In a car with 130,000 + miles....probably still with the original oil pump....and a sludge problem.....I think it imperative to change the oil pump, too.