Oil light help

Ok so my sister bought a 1998 2.2L Cavalier about 2 weeks ago. Drives great runs great starts great. Well she came home one day and said the oil light was coming on at idle.

Checked oil level it was full.

Changed pressure switch figuring it was bad and problem went away... for about a week and now it is coming on again at idle.

When I changed the switch I ran some seafoam in the oil at idle for about 5-10 mins to clean any crud out of the engine. Then changed the oil with 5-20w sythetic oil.

When she bought the car she was told the engine was rebuilt around 10K miles ago. Possible it wasn't rebuilt?

Any ideas would really help, thanks.


EDIT: Also when the oil light tends to come on the temp guage is near the top end (About 3/4 mark or more) and the rad fan doesnt always come on light I think it shound)

Possible it might be overheating? I had the same problem while delivering pizzas in my 99 2.2 . Only when i idle for a extended period of time. In the winter theres no problems.

alright so I put a Mechanical Oil Pressue Gauge on the car and here are the specs:

60 PSI cold start idle
80 PSI cold rev
40 PSI halfway warmed up idle
70 PSI halfway warmed up rev
2 PSI warmed up idle <--- yes that is a 2 :eek7:
60 PSI warmed up rev

So I am pretty sure there is a problem. Any ideas where to start?

Well I am no mechanic,but if it was me I would think the oil pump is bad or something either way the engine needs internal work. Maybe a mistake was made rebuilding (if it was). Too bad

Then changed the oil with 5-20w sythetic oil.

I'd start by draining that and refilling with 5/30. Might be getting too thin for the pump, which may not have been replaced with the rebuild.

- alright I pulled the oil pan today and plastigauged all the main bearings and rod bearings and they are still good with little wear less than .004in (Looking good for the rebuild)

- Looked up past the crankshaft and the cam shaft looks brand new so im going to figure those bearings are good also.

- pulled the oil pump and the gears have very little play between them but the clearance between the gears and the walls of the housing are less than .005in

- oil pump pickup screen is sitting about 1/2 in off the bottom of the oil pan.

- Replaced the oil filter (Fram) with AC Delco and put in 10w 30 non synth oil.



But still the oil pressure is at maximum at operating temp only about 4 - 5 psi if lucky. And on occasion the new oil pressure sending unit still trips the oil light from time to time at idle (Going off T-fitting from oil pressure gauge.

Possible bad oil pump?

Could it also be a pressure relief valve that is dirty, or has a bad spring?