Hey guys,

ok ive been having problems with my car recently...I changed out the thermostat and fan switch (coolant poured everywhere, including over the exhaust)....

And then I was messing with the screw on the passenger side of thee carb (thought it was the idle speed screw) but then found out the idle screw is the one attached to the gas thing, so I was trying to adjust the idle...but it wast going anywhere...

This morning when I started it up, the RPM jumped to about 2500 and stayed there, and tehn I turned the key off after about 5 minutes(waited for it to warm up) the car kept sputtering, for about a minute, until a pop with a little tiny bit of white smoke came out of the carb...


After that, I restarted the car, and it ran fine...weirdest problem ever...

Now, since then my idle jumps up and down RPM...the engine seems stable but the rpm moves about a quarter of an inch up or down.

The idle screw doesnt seem to do anything..

I have the car where it fires up around 700 RPM...but it goes up and down between about 850 and 600... and then, if you press teh gas in for a few seconds, and then let the rpm drop, it goes down to about 1000 but does the same up and down thing... but if you tap the gas it seems to go back down to 700.

I personally like the 1000 idle, but i have to pass emissions test and one of the visual test is that idle has to be manufacturers spec.

So 1) can someone explain how to properly adjust the idle..do you just turn the screw? why doesn't it seem to do anything?

2) what is the screw on the passenger side that looks like the idle screw? did I mess something up by adjusting that?

3)anybody know why my RPM wont stay stable?

Thanks guys!!!

86 z28 Camaro with 305, almost 100% stock

 

What carb?

 

um...normal stock carb im pretty sure...

 

Maybe a vacuum leak causing the idle to surge up and down.
Don't know why the idle adjustment screw has no affect.
Idle at 1k is not good. It will cause the engine to "diesel" after you shut it off.

 

Checked for vacuum leaks...couldn't find any...wouldn't the service engine light come one if there was a leak?

ALSO, does the screw adjust idle AUTOMATICALLY? or do I have to reset ECM, or turn the car off and on? or what?

Ok started it up again after 24 hours, and it ran kindof fine, but IDLED REALLY LOW, like 450...and then once it heated up, it slowely climbed to 1000 again... it was somewhat bumpy and unstable (no t that much though)

but once it heated up to about 220, it ran perfect beside the 1000 rpm idle..

WHAT IS GOING ON

thanks for your help!

 

The 'official' procedure should be on your emissions decal. The unofficial way is to just turn the screw in or out until it idles the way you want it to.

This is you FAST idle adjustment. It adjusts your idle when your engine's cold. After your car warms up, this fast idle system 'disengages' and your idle rpm is now contoled by your idle screw on the drivers side of the carb.

Note, there are multiple 'steps' on the fast idle cam. I'll assume you have 3 steps for this demonstration;

Think of your fast idle system as having a SUPER fast idle, REALLY fast idle, and FAST idle settings. Start your car up in the morning, it will be on SUPER fast idle upon intial startup. Give the throttle a blip and it will fall to REALLY fast idle. It will probabaly stay there until the car warms up a bit and falls down to FAST idle. Eventually you end up at normal ( CURB ) idle.

Again there is a proper procedure for setting it, but for now just set it so your car can idle and drive good during a cold start.

Probabaly a well hidden vacuum leak somewhere. Maybe a lazy O2 sensor.

 

The o2 sensor was replaced about 2 months back along with a full tune up, plugs, wires, cap, rotor, almost everything.

Ok, everything you said makes a lot of sense...I thought there was one idle screw, but it would explain why my cars Idle acts weird when cold and why it ends up at 1000...I was probably trying to adjust the curb idle when the engine was on fast idle...

ANYWAY...where is the adjustment for the SUPER FAST idle? I think i can get it working now that I know the curb idle and fast idle.

And also, does the car go to fast idle when electronics are on such as the fan or the AC?

and just for clarification...Turning the screw clockwise INCREASES the idle right?

And where is the emissions decal?

thank you so much!

 

All your fast idle steps are adjusted by the same screw on the passenger side.

Not really. I'm not famililar with your exact car but usually when a power robbing accessory like the AC is turned on, an electronic solenoid ( on the drivers side connected to the throttle bracket somehow ) will engage and manually 'push' your throttle open more than your curb idle setting.

Yes.

On a G-body, they're on the radiator shroud in clear sight. I don't know where they are on an F-body car but always assumed they were in the same location. It could have been removed.

Here's an example of what you're looking for; http://members.dandy.net/~k0xp/Oldsm...decal_Full.jpg