My 81vett really high idling ,looked at the manual book say it control by computer. Is ,there a way I can lower the idle ? this is new for me.Thankyou very much for your will be responses. :smash:

 

Has it always idled fast, or is this something that just started? The idle is computer controlled, to a point. The thing is that there is an idle set screw that can be adjusted, and usually that works just fine, but in some cases the mixture control selenoid rich and lean stop adjustments need to be "massaged" a little. It all kind of depends on if this is something that just started, or if it's always been that way, and if it has been that way whether or not somebody was "working" on the carb before. Some people who like to call themselves mechanics do some pretty funky tuning on these carbs to try to get them to run. If it just started and nothing was worked on recently, check your computer for trouble codes, check to see what you have for vacuum at the T fitting on the top of the intake, and check your ignition timing.

-Justin

 

Assuming this is a new problem that you noticed, I doubt its a carb adjustment. I'd check the choke on the carb and also look for a vacuum leak.
All the vacuum operated stuff still working?

 

Mine had been having the same problem, it will idle at around 2100 like the choke is stuck, I thought at first that it was a choke link sticking but I found a wire hooked to the passenger side of the carb had come off, when I hooked it back up the idle dropped right away so it must be some electrical part of the tuning for the choke. My emission stuff was removed before I bought it so I assumed the computer is also in-op but evidently this part still functions or has a necessity. Hope that is you problem as it is a real easy fix :cheers:

 

Like Dalannex said, could be the M/C solenoid limits (rich or lean, or both) being out of whack. That usually only occurs if somebody messes with them, which isn't easy to do. However, something else that causes the high-idle problem is very easy to adjust - that is the idle air bleed valve.

Basically, if the M/C solenoid limits are set OK, your idle is controlled by two settings: the idle stop screw ("stop") and the idle air bleed valve ("bleed"). The "stop" is on the driver's side of the carb (I'm sure you knew that already!) on the throttle linkage. The "bleed" is in the very top of the carb, by the primaries; it's a big slotted screw, usually chrome, and originally hidden under a sheetmetal cover. The cover is almost always long gone.

If you back the "stop" out (counterclockwise), the idle should go down. If you've backed the "stop" out until it no longer contacts the throttle linkage, and the idle is still too high, then turn it back in until it just barely contacts the throttle linkage. Then, adjust the "bleed" either in or out, until you see a drop in idle speed. Continue to turn the "stop" in (which raises the idle speed) and then adjust the "bleed" to reduce idle speed, until you get the speed you want, somewhere around 800 rpm. When both are adjusted correctly, you should have the "stop" turned in about 1 or 2 turns after contact with the linkage, and adjusting it in or out a little will produce a slight increase or decrease in idle rpm.

Don't forget that ignition timing affects idle speed, too. Too much advance at idle will keep the idle speed too high. If adjusting the carb gets the idle speed into the ballpark, then you can unplug the computer from the distributor and do the proper timing check and adjustment.

Just take your time, and don't get frustrated with it. If Bubba has been messing with it, it may take some time to get all of the variables back into their normal range so you can properly adjust them.

Good luck! :seeya

 

Before you go adjusting the settings on the carb, make sure the choke is opening the whole way. The choke should be fully opened after 3.5 minutes. Also make sure the fast idle cam is free to move. I had the choke relay in my go bad and the choke would only open half way because the choke wasn't being given any amps, thought it was still getting 12 volts. If your "Choke" light on the dash is on, then there is a problem in the choke wiring (bad relay or wire) :cheers:

 

Thankyou for all yours advides , with all the instructions I was able to lower the fast idle by unscrew the stop screw and found the came of the choke , but like stickboy said my choke light still on that 's mean I had a bad relay so how can I fix this? is the relay inside the choke? more answers ...Please Thank you very much for the helps.

 

To test your choke, disconnect the choke wire, with the ingition on check for 12 volts. If you have 12 volts, but the choke doesn't open hook a wire up from the positive on the alternator (+12 volts) to the choke. If the choke now opens, then it is most likely a bad heater relay. The heater relay is located under the center console right in front of the ashtray on the drver's side. You can get at it by removing the driver's side panel. In mine it was a small green box with 4 wires going to it (2 to the same contact). You can get a new relay from the Chevy dealer. The part number I have is 14089568 and I paid about $10 for the realy. If I remember right I had to break a peg off to get the connector to fit. The choke light should be on with the ignition on, but off when the engine is running. If not then you have a break in the wiring somewhere. I don't have a scanner, but the service manual has a good description and wiring diagram showing how it is supposed to work. :cheers:


[Modified by stickboy, 4:39 PM 11/26/2002]