Hello everybody. I'm new at this forum. I have a 1990 Audi 100 with 98k miles on it. I bought it from a guy who had the car parked in the yard for almost 7 years. It was literally stuck on the ground. I repaired it and I've been using it everyday for almost 2 years now. It works like a charm and, amazingly, looks beautiful after all that time "junked". .A few days ago, when I was returning from a 2 hours trip, I've noticed the "low oil pressure warning" on the dash while I was stopped on a light. I've never had any oil problems before. I changed the oil regularly every 3k miles (along with filter) and checked the level on a regular basis. Problem goes away when I hit the gas again, and only happens when the engine is hot and idling. When I first start the engine in the morning, oil pressure goes above 5 bars for a few seconds and back to between 4 and 5 bars. Idle pressure with cold engine is 3 bars, and driving, between 4 and 5 bars. With a hot engine, pressure is between 2 and 3 bars driving (with engine around 2500rpm, between 3 and 4 bars around 3500 rpm) but drops to 0.5 bars at idle. I was thinking about a bad pressure sender or switch, but (and correct me if I'm wrong) the oil pressure gauge matches the alarm. I mean, the sender controls just the pressure gauge and the pressure switch (white) triggers the alarm when the pressure drops below 0.3 bars. So that, in theory, discards a bad sender or switch. I just changed the oil and filter (just in case) and having same problem. I'm using Castrol 5W30 and Fram TG filter (I've been using same combination since day 1 with no problem at all. By the way, the car uses no oil at all and it's idling at around 750-800 rpm. Is there any way to adjust the idle on this NF engine? Thanks in advance. Any help will be greatly appreciated.

 

Could be a number of issues, but the best place to start would be by getting a mechanical gauge and verifying the low oil pressure

 

And the problem was the oil pressure sensor. For some reason, it was acting up when the engine was hot, "dropping" the pressure. I changed the sensor and it's working good now....