[cavf150]

I have the idle set at 750rpm as indicated on the spec tag under the hood. I have tested and retested all vacuum lines and there is absolutely no leaks. I even used a propane torch not lit of course, and no flucuation in idle. I removed the check valve and replaced it with the same results, and I plugged all ports same same. I am leaning to the booster, and I am guessing that there is a possible leak in the diaphram. I really think that it is a simple fix, but I can't locate the source. Solid mechanic people say that is what the probable source is, however they say it can't be TPS related or the idle would do it constantly. Most I talk to say Tps means throttle only. Brake means vacuum, and if it is , where the heck is the leak! It seems logical that it has to lead to the diaphram in the booster. On the road the truck performs flawlessly, only problem is at a stop w/foot on the brake, take the foot off the brake and all is fine. No other accessories are engaged, and even w/ the ac on and all lights plus, it only does it w/foot on the brake. PERPLEXING TO SAY THE LEAST! Any ideas are of help. The initial start up is fine and it idles back to spec as it should.
I have read all kind of threads about idle problems, and the more I read the more confused I get. I just don't want to throw parts at this thing , because of cost. Well I hope it irons out. Bob
"Remember upon the conduct of each depends the fate of all" Alexander the Great