1985 F150, engine races when idling and now it wont start, any ideas? I will go to a mechanic but its Sunday and I need the truck urgently so thought Id ask in case there is something obvious to check.
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You don't say if the engine is carb or fuel injected. If it has a carb, it could be sticking linkage for the fast idle to the choke. If it is fuel injected it could be a faulty idle air control valve. Or it could be something holding the throttle open like a binding cable.
One common problem is a vac leak or a sticking throttle plate. The computer controls idle speed by how much air is allowed into the intake. The idle control valve could be sticking even tho you have cleaned it, or have a faulty motor.
you didnt say if it was happening only during the initial warm up of the vehicle or all the time. if it is just during warm up this is not too unusual as long as the engine isnt racing. if it is just a "high idle", say arround 2,000 rpm's its normal. the idle would usually go down as the vehicle reaches operating temperature. when you put the vehicle in gear, you are actually loading the engine slightly, thats why the idle comes down then. when in park the engine has no load on it so it is free to rev a little higher at these times. if it a at a high idle constantly, then i would start looking for sticking throttle cable, binding throttle plates, ect and remedy the problem. this should not have anything to do with the dual exhaust.
strip and clean out the carb,or quick fix ,rev engine with air filter off and then hold hand over intake this may or may not not cure it .because when hand is held over carb and stops air the suction will draw any muck through the jets
it will idle real high or possibly not at all you should be able to see if it is leaking by looking around the intake you could also spray alittle either around it while running and see if it itles high if so thats your problem