I spent a good while scanning past threads earlier and couldn't find anything relating to my situation. Yesterday, I pulled into my driveway and sat idling in drive while I checked my phone and noticed something odd. I drive idle at 500, but for only a second or two it would drop to around 480-490 and would feel slightly rougher. I changed to all other gear positions and only experienced it in drive. I haven't had it do it to me today. Truck is an 07 5.4 with 180k. Recently replaced all plugs and coils, fresh oil/filter, new fuel filter, good air filter, clean MAF and clean TB. It's not major enough to warrant me to go crazy about it, but for me, a new noise/feeling generally equals new problem. Just wanting a general thought from you all to see maybe if I'm missing something. A/C is off when this happens, so not IAC.

Thanks~

 

Hmmm, not sure on this one. I will tell you its not your IAC be cause you dont have one. Most likely something electrical kicked on and caused the low idle.

 

Makes sense now....lol

 

Also, do have a slight manifold leak on passenger side. don't think it's enough to contribute and generally goes away when warm.

 

It's likely the notorious low idle ford programs from the factory. Run your headlights and AC and watch the idle smooth out..
A tuner is a great fix to adjust the idle.
Another great fix is 5w-30 and fresh updated VCT solenoids.

 

Thanks Especial, I'll definitely look into the VCT solenoids. (Don't want to get into viscosity discussions lol) I've ran 10-30 since the stone age on the old girl, will switching to a lighter weight cause any issues?

 

Not with a 5w-30.. It will only be thinner when cold vs the 10w-30 your running right now.. Once warm 5w-30 will relatively be the same thickness as your 10w-30 when it's warm.

The newly revised check valved solenoids should help stabilize any rough idle if it's from the low oil pressure created from a low idle speed..

 

Is there a preferred brand to use? Or just go get'em at an auto store.

 

Oem motorcraft.. Your local dealer should have the solenoids and the seals which you will need as well.
If you have an 07+ model than the valve covers need to be removed to change the solenoids. The seals on the 07+ valve covers are not removable..
You will also need a 6" long or longer t56 torx screwdriver to turn the fastener..
If your truck is an 04-06 the job is much easier..

 

When your idle speed went down, did you have your defroster on? If yes, the a/c will automatically kick on and off (even though your a/c is set to off).