So, this has been exactly the same since i bought the car 15 months ago. After the car has been sitting around 6+ hrs and you start the car everything goes perfect, car revs up to around 1500 and drops to around 1300 for about 20-30 secs and then falls below 1000, this is right when I get this annoying clack,clack,clack sound witch usually lasts around 20-30 secs then it goes away, now havent had it dynoed or anything but it runs absolutely perfect, fast and never a prob or a spit or sputter but every morning and everyday after work same noise. Originally i took it to the dealership i bought it from and told them it sounds like its coming from the driver side rear off the motor closest to the firewall and the head mech. told me oh it sounds like a sticky injector from it sitting on the lot for 1 month and to run injector cleaner through it and it would clear up, 6000 miles I highly dought it but gave it a try anyway and just as i thought nope no fix, so i took the car to a friend at the ford dealership in my town, he's good and i trust him. He kept the car for three days and kept in contact with a ford rep and they went through all the steps they could pulled valve cover checked everything under there and checked all oil passages, oil pressure and everything they could do to see if the noise was coming from there and of course nothing so since the noise couldnt be heard from inside the car with the windows up the ford rep said its nothing bad with the engine and is just one of the noises the car makes, nothing bad. But i def. need some insight on what this could be cause i plan on supercharging it and would like to really make some power with it, also the noise almost sound like piston slap but its weird its offbeat kinda like it doesnt match the motor kinda like clack.......clackclack....clackclack...clack kinda the only way to describe it, sorry for being so long winded but if anyone has answers or insight that will help please let me know cause although i really dont feel its anything bad with the motor I wouldnt mind getting rid of it.

 

do you have an aftermarket CAI??? i had the same issue when i first bought my Steeda CAI. It was rattling against the driver's side body panel when i would start it up. It was barely touching so it made a decent rattle but not bad enough to make it easily identifiable.

 

Where is the sound coming from? Front, rear, drivers, passenger, engine bay???

 

sounds like your injectors

 

no only aftermarket mod so far is macs but noise didnt change and with the hood popped it sounds like its coming from drivers side rear, closest to firewall but i just went outside and jacked it up and started it and it sounds like its coming from bottom rear of motor, it didnt last long but almost sounded like it was coming from where the motor meets the tranny area????? F#@$ this is annoying trying to chase this!

 

sorry, not sure what to tell you man....the noise you are describing (clacking) leads me be to believe it's the injectors, but since it can't be heard in person, it's hard to say. if you haven't already, I'd try the search function and see what kinds of results you get...one might lead you to the exact noise that you have..

good luck

 

clacking like this?

this is my car

http://www.youtube.com/watch?v=p9XebxDXYss

 

yeah doode it is kinda like that but it just throws me off because it only does it for a little when its cold about half a min. then it all stops and then it runs alot quieter than yours. Its almost like its only one of the injectors out of the 8, but i feel alot better after work today because a guy at work drove in his wifes 06 f150 and his does the same thing and has almost 50000 miles on it and has done it since day one and the dealership also told him its a common noise with the cold injectors and plastic intakes.