How Fast Should Cold Idle Speed Be?

[Eddie 70]

Well I guess that just about sums it up, how fast should cold idle speed be? Right now it is about 17-1800RPM.

 

[Bob Chadwick]

Mine is 15 - 1700. I thought that this was too high but my mechanic confirmed it as being the right number.

 

[Stallion]

How long does it take for your engines to warm up? I guess it depends on the ambient temp outside?

TR

 

[22229stingray81]

Eddie 70,

Mine goes between 1800 and 2200 rpm, ive been told its a little high, but I have the electric choke on my '81, may be the cause.

Stallion,

On "old" vettes there is a function called "fast idle" in where a mechanism called the choke (on the side of the carburetor) which when your engine is cold, basically races it to about 2000rpm to warm it up, then when it gets warmed up, usually 3 minutes I find, you push the accelerator in a tiny bit and it turns off the fast idle function. Your vette will still lag a tiny bit untill you accelerate a few times because it isnt fully warmed up.. but ill tell you... the fast idle saves you on cold days...


-Tatortot

 

[lytemup]

i believe the fast idle setting for an '81 is 1600 rpm. if you have access to a service manual the setting (and how to adjust) should be in there...although i think the 81s may be on a label under the hood.

 

[qwall]

didnt c3 have a "9th" injector that was designed especially for cold starting, i know i read that somewhere just dont remember where.

q

 

[22229stingray81]

lytemup,

I know the setting is a little high but I prefer it there.. also my mechanic seems to set it there purposely too... I think ill stick with it, it warms up a little faster that way, thanks for the info though. It wont hurt the engine with the few extra rpm fast idle will it? Ive had it this way for about 3 years now... Also, my underhood sticker is unreadable, but I do have a repair manual. Thanks again.

-Tatortot

 

[Gary42]

Fast idle on a '72

I'm glad someone brought this thread up. I was also wondering what was normal. Also wondering how long it should remain there until kicking down to normal idle. On my '72, fast idle is around 1600 RPM. If the ambient temp is chilly, about 50 deg F, it can take four or five minutes to come down. In the summer, at 70 deg F, it takes only a minute or so.

 

[Bob Chadwick]

Doesn't it come down in stages versus an all or nothing thing.

How does the fast idle work on a Q-jet. The only other carburated cars I have workd on have had a bi-metallic screen with a cam.

 

[Red76Vette]

my 76 is 1500-1900 is that okay or a little low.

Thanks,
Chuck

 

[Eddie 70]

I do have an electric choke on mine so it does come down in stages but you have to rev the engine up to get it to come down. Right now it is idling down around 1600. I would really like it to be just a little lower. I am not overly fond of my engine just setting there running away like that.:nono

 

[Stallion]

Can you tamper with the fast idle numbers to lower/raise them, or is it a set sort of thing?

 

[lytemup]

most any carburator allows for adjustment of this, with a screw or rod or some other mechinism