i have a 82 olds delta 88 with a 307 olds motor in it with a 4 bl carb on it.on the drivers side in front of carb there is a fast idle vaccum dash pot thing.it looks like it controls the fast idle on the carb.is there a adjustment on it.i tried to turn the plunger in but that didnt work.it idles a little high and i turned the idle screw down on carb but the plunger wont let it go down any further.any ideas or is there a way to check mine to make sure it is good.thanks Ray ________ BODY SCIENCE
Vacuum or electric? Got a photo? I'd kinda expect it to be an idle solenoid that is energized either with the ignition or with the A/C. If with the ignition, it will prevent run-on, allowing the throttle to shut completely when you turn off the ignition. If with the A/C, it will provide a bit more throttle when the compressor kicks in, so the drag from the compressor doesn't stall the engine at idle. IF it's just a dashpot, perhaps it adjusts by threading the whole dashpot in and out of the bracket???
On a Q-jet, the fast idle screw is buried under all the choke mechanicm stuff on the passenger side of the carb. Look just above or below the end of the throttle shaft. You should be able to get a long skinny screwdriver on it from the front. I forget, but I think the 'right' setting is around 1200-1300 rpm with the high idle cam (the weight that comes up when the choke is cold) on it's highest step, with the engine warm. Once the engine is warm, the choke goes away, the high idle weight/cam drops down, and the high idle screw isn't used. (Regular idle speed is set by a screw on the driver's side, just above the throttle shaft.) Shurkey's right about the dashpot thing, if it's got a wire going to it, it's part of the a/c, and if not, it is there to keep the engine from stalling in gear when the throttle is closed suddenly (it slows the throttle closing to idle).
I believe that you refer to the device called an Idle load compensator. It was originally used to control the idle speed by referencing the load at idle. It is sensitive to changes in the idle vacuum. If the load increases, the vacuum drops, causing a spring to push the plunger slightly outward, raising the idle speed. If the vacuum increases, as it would when shifting from drive to park, the rising manifold vacuum would retract the plunger, reducing the idle speed. On later models, it was connected to a solenoid, which causes the plunger to retract on shutdown, eliminating the resulting possibilities of dieseling. This device was mounted on the driver's side of the carb, with two vacuum ports on it. The center one was used to adjust the device. Ray
Didn't 1982 GM cars have a computer? If so, the idle speed is controlled by the Idle Load Compensator via the computer.
Actually, no. The computer, which controlled the ignition timing, and the carb, as well as the emission controls, did not control the idle speed on this 'Y' engine. It was controlled via the ILC, which was vacuum operated. I worked for GM, both as an instructor, and as a technician on these engines. Its operation is quite familiar to me. Not all of these computer controlled engines were idle speed controlled via the computer. This engine, and the 5.0 Chevrolet engines were examples, though not exclusive examples. Ray
