I changed mufflers, swapping the stock muffler for an aftermarket using the stock tailpipe. I also added a drop in K&N filter. After the mods, I unplugged the battery with the headlights on and let it drain for an hour. I hooked the battery back up, let the truck idle to operating temp, turned on the A/C for 1 minute, and then drove the truck about 20 miles, as the owners manual stated to let the truck relearn its "idle trim". Everything went smoothly and the truck ran well.

The next day, I started the truck and took it for a drive. Everything ran great in the morning. In the afternoon, the truck would not idle correctly. It jumped from 500 rpm to 900 rpm, back and forth, sounding like a monster truck idling.

I unhooked the battery and tried to reset the computer again. The truck now continues to idle from 500 rpm to 900 rpm.

Did I do something wrong? Anybody else have this problem? The truck only has 700 miles on it and I am wondering if I just need to give it some time to relearn its idle.

Any thoughts are appreciated.

 

No you didn't. The only thing you did wrong was to buy a Ford.
My 2001 supercrew has been doing that for a while now, and I didn't modify anything. You were going to see that sooner or later.
Mine goes to 1500 and then back to 800. it won't go away until I floor it once. Your rough idle if it hasn't started, it will. If you don't have extended crank, you will. It will also start smoking after extended crank becouse of the extra gas that will be dumped in the ports. No I am not a gipsy. I have all of the above.
All I can say is take it back over and over again and keep your paperwork in order.
According to Ford all of the above is normal.
When you are done with your 4th and the 5th visit, let me know I will give you the name of my lawyer.
My case is in the court as we speak.
Sorry to do this to you.
I was all exited about my truck when I first got it.
I had only 12000 miles when all went down the hill from there.

 

Interceptor, The K&N probably leaked some oil on your MAF which will cause your idle condition. You will need to carefully clean it with a que-tip. Oh and when you re-set the computer don't let it idle all the way back to operating temp that is bad for it you only need to let it idlefor about 5 min max.

Jundis sorry to hear about your problems dude. Interceptor doesn't have the same problems as you and he probably doesn't need to be told that he will. Mellow out and keep us posted on what happens in court.

good luck

peace-

 

Your idle problem sounds like a dirty IAC(idle-air-control) valve but you only have 700 miles on it so that wouldn't be the problem--unless the IAC valve is defective??? The two mods you installed could not have caused your problem unless you bumped something loose in or around the intake area???

IMHO, your 'relearn' procedure is too complicated and unneccessary. I've changed intake filter kits and numerous chips on my 01 L and all I have to do to accomplish the 'relearn' is to disconnect the neg. battery cable, turn on the headlights(One of our tuners says that just leaving one of the doors open is enough.) for only 5 minutes and then reverse the procedure.

Hope to read what you find to be the ultimate answer.

Dan