Hey eveyrone, I ran into a little problem. My truck has just started idling really low. It will start up then drop to as low as 350 rpms and go up to about 700-750, and it will continue to go up and down. When I am driving on interstate it drives fine. Its only when I slow down or come to a stop that it continues again. I have read about different things such as vacuum lines and even throttle body spacer being messed up. Ohh yea, Truck has 80,000 miles on it, I just installed a Train Horn kit and I just had the oil changed. Another thing my servive engine light just came on today so I am getting a little nervous. It is a 2005 f-150 4.6l. If you have any suggestions on what I should do or look at, I would greatly appreciate it. I am a college kid so I am trying to avoid bringing it to a shop.haha. Thanks. Jason.

 

try cleaning your throttle body, and iac, if that dont help try a new fuel filter or tps sensor,

for the engine light goto autozone, get a code then look it up on google for info

 

Wierd, I kinda had the same issue with my 07 5.4L XLT. There would be moments where I'd be at a stop, or coming to a stop, my rpm gauge would go down to almost 300, then I'd have to give her gas and it would bog like a son-of-a-gun then shot to 2k. I later got an Edge programmer and it did the same thing on every tune. After a while I removed the tune and went back to stock and it went away. All my lines were connected, no leaky hoses, and my MAF and TB were cleaned. I wish you the best man, it's crazy!

 

thanks for the tips. hopefully it will be one of those things and it wont be an everlasting problem. Thanks again.

 

I'd start off by restting the computer and letting it 'relearn' it's idle... But, since you say you also have a CEL already, that's probably telling you what the problem is right there...

You could still reset and see what happens and if the problem is still present, it'll toss out a code again anyway... Won't cost you anything but time!

Mitch

 

I had the same problem about 6 months ago and it was my throttle body that was dirty. I didn't have a CEL, but it's run really well ever since the cleaning. While you're at it, you should clean out the MAF as well. There's a how-to on this site that's really well documented. Get the code from Auto Zone for free to see if there's something else wrong, but cleaning those things will help in the long run anyway. Good Luck.

 

clean MAF, run fuel system cleaner, check air filter, all to make sure it's idling right

 

I wouldn't do anything with it until you have the CEL code read. Go by any AutoZone and they'll read them for free. Get the code number from them, not what they think is wrong- get the number, like a P0141. Otherwise, yer wasting yer time cleaning this and that and not knowing if it is the issue. FWIW, you don't have an IAC to clean with drive by wire.

 

alright. so here it is. tried to run the scan tool and it started throwing out a bunch of erratic codes, come to find out I was missing a 20amp fuse that was making it freak out. After all of that was cleared, ran it again. It gave a a P0300 (random misfire detected), P0506 (idle air valve circuit fault). cleared the codes an then gave a road test. The idle still dropped when I braked. Cleaned out the Throttle body, reset pcm, and had to perform an idle relearn procedure. Now its running normal and NONE of the problems were related to my horn install!!!! WOOHOOOO!!!! Thanks for all of the help again guys

 

Good to hear!

 

It's a good thing cleaning the TB fixed it - those electronic throttle bodies ain't cheap!