Hello all, I have a 03 F150 KR 5.4 4x4. Changed the alt, tensioner assy, idler pully, and belt this past weekend and all seemed fine.... till I cranked up my truck after work today!!! It sounded like i had a dagum supercharger under the hood lol. I was like wtf is that noise and raised up the hood but couldnt exactally pin point what it was. The truck was cold so it was loud then the truck warmed up and it stopped so I have no idea whats going on there. Also since all that was occuring the tachometer was acting funny as if the IAC was bad, when i would roll to a stop it would drop down to 500rpm then back up to normal at 650rpm. Any suggestions would help on this but im thinking on the idle prob is a IAC needing cleaned or replaced. Funny that all of this started heppening after the alternator and other things were changed and i didnt buy the cheap stuff either.

 

May want to have that alternator checked again. I bought a new one and installed it only to have a similar problem.

 

as far as the sounds i heard and the idle, or just the sound with the idle situation being completely different?

 

anyone?

 

Remove the belt and start it. If the sound goes away, it's one of the pulleys. It's best to eliminate those first. I know you have replaced a few of them, but I have seen them make noise when new. Eliminate that and go from there.

 

It was the idler making that noise so I had to find a bolt with one of those washers made on it. I cut the head of the bolt off and drilled the ceter hole of the washer 1mm bigger so it would slightly slip over the threads to space out the big washer so it wouldnt rub the bearing surface. I also got a new alt from Advance for the same price as the reman, the manager discounted it 50 bucks since I have been having so much trouble with this. I also got an IAC while I was there for 20 bucks he also discounted it from 50 bucks. Im not going to put it on until I test out the new alt and new pulley and actually test drive the truck to see if the rmps are doing the same thing. My theory is that the idler was some how interfearing with the belt tuning properly thus making the truck have to work harder to turn that belt. I just hope all this effort fixed my problem if not I guess I will be cussing at the IAC tomorrow since its crammed way back there on the passenger side. Thanks to all who have replied I really appreciate it.

Oh and having a mechanics stethescope relly helped me big time. Sorry ifi didnt spell that right but O well this isint a spelling bee lol.

 

well replaced reman alt with a new alt and fixed the noise issue with the idler pulley. The rpms are still dropping to 500 and then back up to 650rpm. Im wondering if the truck has to be driven a certian amount of miles to reset the computer??? I do have a new IAC in the box but would like to get some additional input from anyone who may have had this same problem, and what they did to fix it. The truck does not act like it wants to stall when it drops that low but have never seen it do that before. I also heard what sounded like a clock ticking noise a few times in the cab but could not pinpoint where it was coming from as it only did it twice. Maybe its the computer reprogramming itself?? Thanks for any further input on this.

 

Pull the throttle body, clean it, and replace the IAC.

 

throttle body is clean, I am suspecting the IAC but its mere concidence that this happened after the alt change. I had a diode staying open on the alt that was not allowing it to charge correctly, could this have some how affected the IAC in any way? m going to drive the truck for a few days to see if anything changes if not I will replace.