[senna21]

On another forum an owner of a 328 is experiencing low oil pressure at idle with the A/C on. His RPMs drop to about 850 and his oil gauge reads almost zero. As the engine picks up revs the oil pressure returns. Here are my questions:

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  1. What should his idle be?
  2. Is 850 too low or is this normally high enough?
  3. Most cars have an “A/C idle switch” that ads more fuel to bring RPMs up when the A/C is turned on. Does the 328 (or 308- injection series) have such a switch?
  4. If it does, where is it and how do you adjust it?

My initial assumption is that his idle dropped to a point that the oil pump isn’t moving enough oil to keep the pressure up. We all know that the 308/328 series gauges aren’t known for being the most accurate so we’ll assume he has more than 0-5lbs of pressure. And yes we’ve told him to check pressure with a secondary gauge just to be sure.

Thoughts. Ideas?

 

['75 308 GT4 (Peter)]

I don't have a 328 Jetronic schematic in front of me, but going from memory, yes, there are some injection systems that have a compensation device to speed up RPM's when the A/C compressor is engaged. Not sure if the 328 has this...

1)His idle should be whatever is specified in his owner's manual. Probably 900-1000RPM
2)850 is on the low'ish side, but nothing that won't keep the engine running smoothly.
3)Not sure (see my comments above)
4)...?... (see #3)

One thing to check: The oil level in the compressor. Maybe if its low, or dry, there could be excessive drag, causing the engine to run harder to turn it (more load resulting in slower speed). I know, that's a long shot...