curb idle vs. fast idle

[sinistral]

engine (CFI) is idling ridiculously fast on startup...

looking thru the chilton's book and see adjustments for "curb idle" and "fast idle"... what's the difference and which should i attempt to adjust to bring this down?

thanks.

P.S. (unrelated)
what is "scottfest"???

[86VickyLX]

Curb idle is the idle that the car settles down to when the car is warmed up.

What's ridiculously fast?
Scottfest is an annual meet for GMN people. People come from all over to hang out, show their cars, drive around, kick back and relax and just have a good time.

[flyb0t]

Curb idle is the normal idle of the car at operating temperature.

Fast idle is the idle that is, well, faster, so that the car can reach operating temperature and just generally warm up. To adjust that, if memory serves, there should be a fast idle cam screw somewhere on the throttle body, my mind escapes me as to exactly where.

[Piece-it pete]

Had the same problem, folks here led me straight to it: front of the throttle body passenger side. I took off the air cleaner, but once you know where it's at you can get it with a long screwdriver without removing the air cleaner.

Pete

[sinistral]

thanks... i'll take a look.

ridiculously fast = ~2,500+ RPMs if i had to guess. i can put it in gear and lurch forward just by taking foot off the brake.

[marquisman]

both fast idle and choke element should be adjusted at the same time.

[Piece-it pete]

How do you do that? All I did was knock the fast idle down a little

Pete

[johnunit]

does it idle at a reasonable RPM once warmed up?

[marquisman]

really, you are setting the choke plate when cold. all you need to do, is loosen the puck back or forth(this will richen or lean out), this will move the choke plate. this way, the engine will run smooth for the time of warm up. for the time it takes, id do it cause, you are already there lol.

[gadget73]

There is no choke plate on CFI. It just uses the pulloff to operate a high idle cam. The only adjustment is basically how long it stays on and it really doesn't do very much of that. It doesn't adjust rich or lean like on a carb. Honestly unless you have reason to rotate that hockey puck, there is very little reason to do it. You might want to verify that its plugged in and that the high idle does drop out though. Sometimes that linkage gets gummy and things don't move like they should.

[1987cp]

I recently read about guys setting a fast idle as high as 1500 or 1800 rpm. But, that was on a carb'd car with no choke that got driven in coldish weather. Guys discussing buying a fancy performance carb with no choke tower at all mentioned the notion of using an A/C dashpot to engage a high idle.

Fast idle on a carb is adjusted by turning a screw that contacts the fast-idle cam. On mine, I have to open the throttle fully by hand to access the screw. Presumably the fast-idle cam on a CFI throttle body works similarly?

+5000 on making sure the fast-idle cam is disengaging properly.

[gadget73]

yeah, it works almost exactly the same as on a carb, just no choke plate over the holes. You either have to manually trip the thing into high idle if the heater has already pulled it off, or it will more or less set itself if the thing is cold. Gotta do the pump throttle to set it bit and all that. Screw on the pass side is high idle, and I want to say you adjust the dashpot itself to set the low idle. The dashpot can also bump the idle up, so that has to be checked to make sure someone hasn't hotwired the solenoid or hooked up the wrong vacuum line to it or some nonsense like that.

[sinistral]

thanks guys

once we get back above 0˚ i'll take a look...