Why does the idle fluctuate..... I'll give as much info on the problem as possible hoping I we can figure it out. 84 K5, 350, Q-jet carb. During the warm months, no problem. When it's cold, problem. I have no heat riser, no smog devices, no EGR, no warm air duct, etc. KN filter sitting on the carb with an electric choke. When I first start up, idles on high as it should, kick it down and it idles around 700. Drive around , come to a stop and the idle goes up to around 1100. Kick it down and it's 700 again for a few minutes then again to around 1100. The carb gaskets are tight, saturated the hell out of the carb area with carb spray looking for a leak, none found. The vacuum advance is hooked up to vacuum at idle port. The power brake vacuum line is connected as is the choke pull off line. All other ports are plugged. I'm using a KN air breather for the valve covers so no PCV. When the engine is warm, the choke is fully open. So, I'm confused as to why the idle fluctuates. Any ideas? Thanks! Could using the open air cleaner cause the idling problems? It's COLD here! It's so cold that we can hang meat outside!