Had a weird experience today on the way to work.

I had just gotten off the highway (cruising about 10 miles at an average of about 70 mph) and was stopped at a light. Usually when stopped at this light the car idles at 900 rpm, the Oil temp is slightly above 200F and the Oil pressure is around "1".

Today the idle dropped to 600 (no cough or any abnormal sound). The light turns green and we move about 150 yards before stopping again. The idle is still at 600 but now the oil pressure gage is swinging between "2" and "3" and oil temp is right on 200. This pattern repeats for about 5 minutes each time I stop at a light.

Then it all returns to normal. Engine revs are back at 900 at idle. Oil pressure tracks with the tach (i.e., as I accelerate 1,000 rpm, 2000 rpm, 3000 rpm, 4000 rpm) the oil pressure corresponds (2,000 rpm = "2", 3000 rpm = "3", etc.). Oil temp is between 200 and 225 were it normally is at that part of my drive.

When I got to work I checked the oil level (at the upper hash, not overfilled) and all fluids looked good. No leaks, no smoke, no abberant noises, no CELs.

I called the dealer and they said since there are no codes (CELs) the only thing to do is monitor. They did say the the oil pressure would increase with the decreased rpm and that it sounded like the A/C compressor had kicked in (but the A/C was off as ambient temp this morning was 64F).

I know it is hard (if not impossible) to diagnos a problem via the forum but any suggestions on avenues of investigation would be appreciated.

Two other notes. The car has ~ 107,000 miles and the oil was changed in July at 104,000 miles.

 

When AC kicks in idle increases couple hundred rpm not decreases. Wait and see sounds like it makes most sense. In meantime you could check battery. Weird stuff sometimes happens if it's not up to snuff.