Sounds like there's nothing wrong with the oiling system, just a normal response to engine speed too low.
The idle part you're referring to is called the Automatic Idle Speed (AIS) motor. They don't fail very often. The place to start is to have your mechanic test drive the car with a hand-held computer called a scanner connected. It will read out, among lots of other stuff, the number of "steps" the engine computer is commanding the AIS motor to.
The steps range from 0 to 256. This is not a typical motor in that it doesn't spin rapidly like a fan motor. The computer pulses it with various voltages and polarities to carefully place the armature in specific positions. As it turns, it opens or closes an air valve on a screw thread. Step 32 is a typical number for a properly running engine. If you see a number closer to 0, the computer is trying to slow the engine down. If it displays a higher number of steps, say 50 to 100, the computer is trying to bring idle speed up. You have to figure out if the computer is trying to do the right thing.
If idle speed is too low, and the AIS steps are unusually high, the motor is not responding or the air passage is blocked with carbon. Something is preventing idle speed from increasing, and the computer sees that and is trying to do something about it.
These clues will give your mechanic an idea of where to look for the problem, but he will have to catch it while the problem is acting up.
Thursday, February 25th, 2010 AT 1:47 AM