I have a 2004 Supercrew with the 5.4 Recently I removed the battery and the truck sat for a few weeks. I needed to move the truck a few times so instead of taking the time to reinstall the battery I just hooked jumper cables up to it, thinking the alternator could power it fine. I finally put the battery in it and now the idle is eratic and the engine sometimes dies when I come to a stop light/sign. I am thinking there is a glich in the computer because of what I did. Maybe just a computer reflash? Is there sometime I can do to reset the computer? I have never had a problem with this truck until I ran it twice without a battery Any ideas? Thanks

 

It's a safe bet that you cooked the PCM. Never EVER run a computer controlled vehicle without a battery.

 

yeah pcms cooked...they have a 70k warranty I believe

 

if it is the pcm, your looking at a $669 part from ford, i've had mine replaced....

 

Cant they just reflash my PCM? The truck runs fine over 1,000 RMP. Its just the idle being shaky and cutting out. $669 I guess thats not too bad. I was expecting the computer to be a couple grand.

 

How long has it been since you reconnected the battery? When the battery is disconnected the PCM looses its volatile memory which is where the settings are stored for the idle characteristics, as a result the PCM uses the default idle settings stored on the EPROM until it can adjust the idle settings itself which can take as little as one drive cycle (if you follow the procedure in the owners manual) or it can take over a week if you never drive more than 10 miles at a time.
It is a pretty safe bet that your PCM is fine. When the PCM fries the engine will not run.

 

This isn't always the case. Running the engine with just jumper cables and no battery is a sure fire way to hurt the PCM. The static discharge from your finger can destroy it, it really doesn't take much. I've seen cases where the PCM was damaged but the engine still ran, but very, very, poorly.