Saturn idle RPM changing according to speed

[Fourthbean]

I just picked up a 2000 Saturn SL. The idle speed will sit at 1200 if I am moving in neutral, if I come to a complete stop it will drop down to 5-800rpm. I was watching it and I think it keeps the rpm's higher when your speed is higher. Can anyone else confirm this? I was slowing from 30 and it was sitting at 1000 or so and then would make a sudden drop to 800 when my speed decreased to a certain point.

This doesn't seem so great for fuel economy, I guess I will be coasting without the engine running in the first place so this won't be too big of a deal.

[cfg83]

Fourthbean -

Originally Posted by Fourthbean

I just picked up a 2000 Saturn SL. The idle speed will sit at 1200 if I am moving in neutral, if I come to a complete stop it will drop down to 5-800rpm. I was watching it and I think it keeps the rpm's higher when your speed is higher. Can anyone else confirm this? I was slowing from 30 and it was sitting at 1000 or so and then would make a sudden drop to 800 when my speed decreased to a certain point.

This doesn't seem so great for fuel economy, I guess I will be coasting without the engine running in the first place so this won't be too big of a deal.

Yup, I think we had figured that the ECU/PCM keeps the idle higher at higher speeds. On my SW2, I am between 800 and 900 RPM while idling at a stop. On the freeway, when I glide in neutral, the RPMs are maybe 1100-1200.

CarloSW2

[cfg83]

Fourthbean -

Here's where we talked about it :

Idle speed control valve
http://www.gassavers.org/showthread.php?t=2852

CarloSW2

[1993CivicVX]

On my VX it's the opposite. At speed it bounces up and down from 600 to 1300 and when I stop it will often rise 2000 and stay there. Odd thing is, it will only go to 2000 and stay there if the car had been cold when started. If you turn the car off and back on again, it will hover around 1200.

[GasSavers_Red]

My TJ does that as well. If I'm coasting 30+MPH but under 60 MPH it will bump the idle up to 1200 RPM and it will bring down it down linearly with speed.

[Fourthbean]

Ahh, so this seems to be a pretty standard feature with cars now a days. Makes sense really, I am sure it saves clutch wear for anyone who isn't careful to rev match when changing gears (like me sometimes).