For anyone with a 5.4L with rough idling and stalling problems, try this. My 5.4L F150 was idling very roughly, fluctuating rpms at idle, and stalling at idle and low throttle settings. The dealer replaced my plugs, I replaced the air filter, idle air control valve, and differential pressure egr valve, all with no results. Then I read a thread on here that said check for PVC hose leaks, so I did and found nothing near the pcv valve. Then I checked all the way back from the PCV valve to the very end of the PCV hose on the top back of the engine(right where it connects to the engine beside the idle air control valve) and found the rubber boot on that end of the PCV hose had melted almost completely in two. I got a new hose from the dealer(includes the pcv valve and boots for both ends(auto parts stores didnt have it), put it on and it totally solved my problem. Engine runs like new again, even with 146000 on it. Perfect idle again. The back of the hose where the elbow boot is that melted is hard to get to, unless you get up on the engine almost and reach far back along the hose until you find where the faulty boot connects to the engine near the firewall. Hope this helps those with similar 5.4L problems!

 

Did you happen to notice a humming or whinning sound every now and then?

I have the humming and whinning sound and the past few days, Ive started to notice a rough idle.

Ive cleaned the IAC valve and the butterfly on the intake, and the humming and whinning is still there.

I was wondering if this and the rough idle are related some how.

Thanks,
Alan

 

Good Job, I'm surprised the dealer didn’t pick up on that. It's a classic 5.4 issue. It comes with the codes P0174 and P0171 System lean bank 1&2. Before you spend money at a the dealer, In the future, invest in a code reader or have Autozone pull the codes then search or post the codes here. It would have saved you a lot of aggravation and money.

 

PROBLEM IS STILL HERE?!?!?