I just bought a 99 a4 and it has been nothing but problems ever since. I bought it with a broken timing belt and rebuilt the head and put all updated timing parts in. All was good besides the oil light came on, so i replaced the oil pressure sending unit. the light still came on, So i pulled the pan and it was a little sludged but the pickup was not clogged. I bought a new oil pump with pickup and replace it today, but it still comes on. I put an oil pressure gauge in place of the the temperature sender. Before when it was cold i was getting at the most 40 psi at the most then when it warmed up it wouldnt go above 20 and at idle it was around 10psi. So when i replaced the pump and first started it shot up to 80 - 90 psi. at idle its around 20 psi and cruisin around 30-40 psi. I checked the wire going from the sender to the connection in the ecu box with a continuity tester while wiggling the harness and it never lost broke its connection. What do you guys think i should test now. This thing is pissing me off and i only bought it for a good daily driver since my nissan eats way too much gas. please help Im lost and dont know where to go from here. Yes i searched and nothing matched my cituation.

 

hmm

According to the FSM you need 14.5 to 50.75 psi at idle and 72.5 to 101.5 psi at 3K RPM.

It seems that you're good at idle but once you reach a higher RPM you are struggling to reach the proper pressure. I'll think about this....

 

i dont know The light comes on a 25 psi evertime. It doesnt makes sense to come on at that pressure. i dont know maybe the switch i got was bad.

 

you might try a can of seafoam in the crankcase, and if you arent already using one, get an oversized oil filter like a mann or mobil1 m301. if the pump is new, the pickup isnt clogged, then there has to be some reason oil isnt flowing, like a clog somewhere in the engine.

what engine is this the 1.8t or the 2.8?

 

but i get great pressure when cold. If i had a clogged port wouldnt the pressure be better when warmed up since the oil gets thinner the hotter it gets. its the 1.8t

 

I wish I could help, but I too am having an issue with my oil light coming on. Keep us updated.

 

When was the last time you replaced your oil filter and which one are you using?

 

I have about 50 miles on all the recent work. I replaced the filter with a napa filter, i cant recall the number maybe a 1393 something like
i think im going to try pulling off the oil filter housing and see if there are any obstructions.

 

Get rid of the Napa filter and buy an Audi OEM, Bosch, or Mann replacement to start. You'd be surprised how much a cheap oil filter can affect your oil pressure.

 

Any of you guys ever use K&N oil filters? No one has mentioned them, so I wondered how the ranked. I'm using one now....they're HUGE!