Just bought 07 f150 lariat 5.4 couple months ago and noticed rough idle when the a/c was on. Found in the owners manual that if the battery was disconnected that you had to go through a process for it to learn idle/fuel trim process. Did the process and it worked but on the rough idle but the throttle response and acceleration was not like i thought it should be. I drove another ford with the same 5.4 and 3.73 rear and it was extremely responsive and great acceleration....now i knew something wasn't right. After calling around to multiple dealers and they all trying to get me to bring my truck in to make money off me i finally talked to one today that was very helpful on the phone. Here is what they told me that i didn't know......" when the battery has been disconnected or replaced that it also affects pcm process with your throttle body which affects your throttle response and acceleration issues". They said they have seen multiple issues where this has caused the throttle body to be replaced. This has caused symptoms of rough idling, poor acceleration, loss of power, trucks stalling out etc....my engine light has not come on yet so here is what they told me to try to do to fix it before i brought it in to the shop. " disconnect the positive terminal for at least 30 min.....reconnect.....start the truck and drive it hard (do not baby it) so that the pcm can relearn the throttle response." they said the pcm's on these truck will regulate themselves to your driving habits. I was wondering if anybody else has tried this and if it worked? My truck is not a daily driver so i wont be able to try it until tonight when i get home.

 

Hmmmmm....i guess its possible due to everything being electronic in these trucks that it could affect it. Id probably give it a few weeks of regular driving to allow it to "re-learn". I would assume since its not a regular driver it will take longer for it to "re-learn" since you dont drive it alot. Also maybe try to clean the TB. Its pretty simple and well worth it in my opinion.

 

I recently had an issue with my 2004 5.4 v8...bad throttle so we replaced that and two days later my trans starts grinding....
Anyway the trans guy told me that the PCM relearns itself basically one way to do it is get the truck up to 55MPH and let it coast till it's literally at 0. But he doesn't think that it's necessary as it will eventually learn this from regular driving. Don't leave a bad throttle unattended because it may have been the cause of my trans to go...or it could have been a symptom...either way it'll turn into a big issue.

 

Good info. I just got this truck a few weeks ago ('07 XLT 5.4 crew) and the acceleration stinks and at idle there is some rough idling. Going to try that and see if it helps.

 

It has been a couple weeks since I did the idle/fuel trim process but only disconnected the battery for about 10 min....so I have seen no change in the throttle response so I will try what they said this evening when I get home and see what happens. If no change I am taking it in to get throttle body replaced. Its covered under my extended warranty so no big deal to me except for the fact that the dealer is an hour away from me.

 

my truck sit for a few days with no battery in it one time.... and when i put one in it and started drving it..it would die all the time... so i d/c it again waited awhile and then drove the ***** off it... and it never gave me any probs

 

I did it last night.....Don't know for sure yet if it has helped......I d/c battery and let it set hooked it back up and let it warm up and drove the hell out of it for about a hour before i turned it back off......didn't have a chance to drive it anymore last night so i will see tonight.......

 

I am not sure if you already saw this, but there are instructios on how to complete the drive cycle in order for the PCM to re-learn. Check here>> http://www.obdii.com/drivecycleford.html. Per these directions, it looks like driving the hell out of the truck will only make the process longer. Also, if your fuel level is not between 1/2 and 3/4, some monitors will not even run.