|
I think cold is a factor because the engine is actually working that much harder. On my Honda, my normal idle is 21-22, but when I start the engine on a cold morning (<32 degrees), it's 16-17, and then when I let the clutch out in neutral, the extra drag of the cold transmission lube drops the idle to 14-15. Also, higher altitudes seem to reduce vacuum as well, probably because the engine needs to work harder to get the same amount of oxygen in.
|