setting idle speed with programmer

[07Expy4x4]

I recently bought an SCT Livewire programmer and got a custom economy and a custom performance tune made for it. The Livewire allows me to change the idle speed in drive and in neutral. In neutral, my stock idle speed is about 625rpm. In drive, the idle speed is about 550rpm.

Would there be any negative effects if I lowered the idle speed in neutral? I was thinking that I could at least drop to 550rpm in neutral since that is what Ford lists as the idle speed for the 5.4 in drive. Is there any need to have a higher idle speed in neutral than in drive? I know the alternator might charge a little less at a lower rpm, but all my electrical and audio is stock, so a slight drop in alternator output probably wouldn't matter.

I am trying to save a little gas when the motor is idling in neutral in order to run the A/C. I have 3 little kids in carseats, and when my wife has to run into a store while I stay with the kids in the truck or we have to pull over and change a diaper, etc, I have to run the A/C in the summer heat (it gets well over 100 degrees in Texas). Just looking for any way possible to save a drop of gas...

 

[07Expy4x4]

25 views and no reply? I guess everyone is interested but doesn't have an answer. Unless someone has some experience lowering the idle speed, I will just leave it alone since the fuel savings would be minimal.

 

[GAINMOB]

I have superchips..depending on what setting...its down to 600 rpms


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[IAExpy]

I'm no expert, and maybe this is dumb, but at some point wouldn't you be low enough to no longer be charging the battery, so even at idle you're just sapping battery power?

 

[07Expy4x4]

Yeah, those were my thoughts as well. I think at some point the alternator wouldn't charge enough, but I have no idea what that point would be. I just got to thinking about it when I realized that the idle speed in drive is lower than the idle speed it park/neutral.

 

[FordandPolaris]

If you have a volt meter, lower the idle speed, and then check the battery terminals. If you read about 14v, then it will charge correctly. Honestly, for as little gas as you will burn idling 100 rpm's faster, I would just leave it alone.

 

[Captain Morgan]

+1, agreed.

 

[trdragons44]

I would personally not change a thing except I would raise drive to 625 or 650. I don't like how low mine idles in drive. With the ac compressor kicking on and off i have seen as low 450.

 

[FordandPolaris]

Dragon, your truck should idle around 6-700 anyways. Try looking into the vacuum leak problem if you haven't already. It should idle higher than 500, even in drive.

 

[trdragons44]

It usually sits around 500-550 but in the middle of summer on a 100 degree day it sinks to 450-500.


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