I have a 2004 with the 5.4L and after the engine is warmed to operating temp, when I am sitting at a red light with the truck in gear, my rpm readout is between the 500 and 750 marks on my tach. I have been trying to figure out this slight rough idle under the condition above, and I have just about come to the conclusion that 625 rpm's is just too low. All I can figure is the PCM is telling the engine to idle at 625. When I manipulate it to 750, all is smooth. Do any of you have the same situation? Does anyone else agree that my rpm's are too low. I have done everything I can think of such as change out plugs and COP's, cleaned MAF sensor, cleaned throttle body, new clean air filter, etc. The only thing I haven't checked is for a vacuum leak, but I don't think that is the problem. Is there any way short of buying a programmer that I can adjust the rpm's up enough to get rid of this slightly rough idle when stopped and in gear? Is there a specific rpm the engine should be under this condition?

 

have you checked that little foam gasket around the filter tray? that has been known to cause trouble

 

Yes I did. AAMOF, I'm the one that drug that thread up from 2007. Definitely made the engine sound better, but no effect on the idle. Do you know what the correct rpm's should be? Maybe I need to take it to Ford and have them reflash the PCM.

 

mine idled around 700-750 IIRC

 

Thanks, that's the kind of info I am looking for.

Anyone else care to share what their 5.4 3 valve idles at?

 

Mines Idling around 500 to 650 and yes its just a bit rough. I almost didn't notice.

 

My '05 FX4 idle around 550-600 and it sucks because it feels like it's going to miss every couple seconds. It seems to drive just fine though and no CELs I just hate how rough it idles so I've been pulling my hair out trying to figure out what's wrong.

 

Mine used to idle at 550-625 and I didn't like it. I did the foam repair and it helped a little. I ended up with bigger tires and an Edge Evo--and adjusted my idle to 675 which is way better. Like you, I tried to research and do anything to bump up the idle without any good results. Sorry, but the EVO was my only solution. (but so worth it!!!)

 

My 4.6 does this at 650 but on rare occasions it will idle at 700-725 I line it when it's up in the 700 range as it seems it has a little more kick off the line

 

Mine idles between 550 and 650, no rough idle though. I did fix the weather stripping around the airbox about 750 miles ago, fixed the noise I had but idle stayed the same.