What can I try next?
I have recently replaced the battery. Every time I want to start it, I have to
boost it. It won't idle down just races like crazy even if I let it run for 10-15
minutes. And after I shut it off I have to boost it again. It started doing this
about 2 or 3 months ago.
Check the alternator sounds like it is bad,the idling issue could be a vacume leak.
First off you have a major draw on the battery, recharge the battery and then do the battery draw test to find the culprit that is killing the battery, as with all Fords start by electrically disconnecting the alternator, if the test light goes out then bingo you have your culprit, if not then proceed. After you fixed the draw then set the park brake and block the wheels, start the engine and then put it in gear if an automatic, if not an automatic push in the clutch and hold, then turn everything electrical on and let it idle, the idle should start to come down and stabilize after a few minutes, if it doesn't then look for a major vacuum leak and also check the ISC unit, it maybe stuck.
Search Ford F-250 Questions
Ford F-250 Experts