Another High Idle Problem
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Another High Idle Problem
Ok, I have a 94 F350 with a 460. It idles at around 1500. If I leave it idling I can stand there and listen to it go from a normal idle to racing at 1300 back and forth. It will continue changing just sitting there running with nothing on(as in a/c or anything else).I have read posts on this until my eyes were crossed. I have tracked down and fixed 3 different vacum leaks. I just cannot find anymore. I have disconnected,pinched,sprayed and done every other trick to try an find another with no success. I did notice that the pcv valve was rattling so I change it and the rattling stoped but did not help the idle, if I pinch the hose the idle will come down slightly. Another thing I just noticed is if I pinch the hose just below th Idle control solinoid(Center of the intake just below the two tubes that come from the air cleaner)the idle goes to normal. This hose goes from the intake to a round empty cannister up to the hoses that connect to the air cleaner. At this point I am lost. I have already replaced the idle control solinoid. I hope someone can she some light on my problem
Thanks
Jim
Thanks
Jim
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Does anyone know why when I pinch off the 1/2"hose that runs fron under the idle cotrol solinoid the the air cleaner hoses the engine will ide normal? Ther is a small cannister im the line but ther is no valve inside it is just an flow thru cannister.
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ok, I will try piching the hose while spraying to check for a leak. Maybe that will help me pin it down.
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Cargo Master
Joined: Sep 2004
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Those vacuum reserve cans can rust through or even the hoses themselves can get hard brittle like plastic and then no longer seal to whatever they're attached.
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Sounds to me like the vapor recovery charcoal cannister and solenoid valve. If my vapor recovery system on my 302 is anything like that on the 460, that is. If the vapor recovery valve sticks open, that will act like a vacuum leak. I don't remember the exact operation of the valve, but someone else will be SURE to correct me if I'm wrong. If I remember what I've read, the valve opens when the throttle is above idle, but closes at WOT, much the same as the EGR valve operates. This pulls vapors from the carbon cannister usually mounted on the sub frame below the battery. That, in turn, has lines going to the fuel tank to capture vapors from the tank and reduce emissions from unspent fuel vapors. But, in short, if you pinch off that line, and the idle drops, sounds to me like it's getting air in there when it shouldn't, and you may have already found your problem.
