Is a jumpy bumpy idle normal in a 5.4?

[71Rcode]

Hi everyone, just to say I've had a CEL-free 18 months out of our '01 5.4 4x4 Expedition (108k to 113k on her in that time). And I love this truck! Reliable, consistent, roomy, not a leak anywhere and fun to drive.

My question is this: the idle (guesing around 800 rpm) in park/neutral is a bit jumpy, as in the idle drops a hair as if a few cylinders are missing intermittently. There is no hint of this under power of any kind (accelerating or at speed), and maybe a slight hint of it in gear (at idle). The previous owner changed the plugs around 100k and said all the COPs were new. I haven't pulled any plugs or COPs for a looksee as there have been no check engine lights. I only fuel her up with the cheapest 87 octane I can find, btw.

These items have been on my to do list. Am I missing anything to check? Or should I do these in a particular order? Thanks!

• replace fuel filter
• injector cleaner (techron) or seafoam
• clean IAC and throttle body
• check all vacuum hoses

 

[rtbrjason]

I notice a bit of a miss or something only at idle. When we pulled the heads off, 2 or 3 of them were clearly running much leaner than the others as per the more whitish color. I should have probably replaced injectors while I was at it, but running 4 bottles of techron (2 separate tanks) seems to have mostly cured this for me.

I would also spray out the throttle body (deep creep by sea foam is my choice here), check vacuum lines and replace fuel filter as those are all cheap and easy things to keep the truck running great.

 

[71Rcode]

Sorry for my delay in responding, Jason. Thanks!

 

[tonydiv]

A dirty IAC can cause this.

Also this can get more pronounced when the air conditioning (or defroster) is on, as the iac will bump up the idle to make up for the additional load on the motor.