My f-250 super duty 5.4 idles like crap, but speratically. not all the time. worse in colder weather, come to a stop, and idles down to about 500. way too low! changed the o2 sensor that was the code she kicked off. next day, came back on. maybe dirty throttle body, or IAC valve? any tips appreciated.

 

Did you look for any vacuum hoses that might have come off?

 

I have a 2003 Taurus. For the past couple days it has been leaking anti-freeze and running hot, but not to the point to ehre the needle goes all the way into the red. The puddles underneath the car are orange in color. Yesterday while driving to work the car started running hot I switched on the heat and the teperature guage dropped the smell of antifreeze was extermely strong and the heat turned cold. After that the car shut off while ddriving down the expressway. We had to car towed home changed the water pump and now the car will not start. It turns over but will not fire up

 

First off, I would suggest you recheck all your work to see if there is anything you forgot to reconnect.
If a thorough check reveals nothing then start with the basics of do you have spark and fuel to permit the engine to run?

 

well.... replaced IAC, and the idle is alot better, for alot longer, but after a good couple mile run at 55 or so, when I stop fully, it wants to drop a little low, the shuddering starts then. used propane, and throttle body cleaner, to look for vacuum leaks, but none found. maybe MAF? visual inspection tells me nothing is wrong with it, but any other tips appreciated......also, will the check engine light go out right away when the problem is fixed, or does it have a series of key cycles it must go thru?

 

I also cleaned throttle body........My buddy hooked up his machine, and it said both bank upstream o2 sensors reported lean fuel trim. MAF?

 

What were the fuel trim readings at idle and then at 2500 RPM ?

 

hankey.....I did not record those readings, but will recheck. What readings would make you suspect what problem? I will certainly check trim readings at idle, and then at 2500rpm. Could you possibly shoot me an idea of what readings will indicate what problems. I have now replaced IAC(it was pretty bad) cleaned maf, cleaned throttle body, changed fuel filter, and been checking daily, for vacuum leaks. The shudder and loss of power speratically, while driving at higher speeds, makes me think could be a fuel issue, but i don't know. I do know that I could hardly blow through the fuel filter, and I am just guessing, but may have failing fuel pump