Hello all!
Got a weird problem with my new F250 with the 6.2. It has a loping, hunting idle. There are no codes present and it runs good with the power to pull my work trailer. The tail pipe has a lot of carbon on it which I think is kinda strange. The valve train sounds OK, no ticks or any bad sounds. The truck is still under warranty and I am going to bring it to the dealer but just wanted to see if anyone has seen this problem before so I know what I am into.
I tried an idle relearn procedure that I saw in youtube and it got a little better but still not right.
Thanks for the help and suggestions, hope somebody has seen this

Bubba

 

Mileage? Any sparking from the coils?

 

Could be plugs or maybe the maf sensor. Miles on truck? When was it last service?

 

The truck is new, with 7K miles. It has never been to the dealer. I had done the idle relearn procedure to it but the idle still hunts around and "lopes" , rpm changing up and down a little. It runs good otherwise and there are no codes present. Figured I would see if anyone has the problem so I would know what to expect when the I get a chance to take it in for warranty service. Just wondering if anyone else had this problem and what it was? I am hearing this whistle on the left side of the steering wheel behind the dash when the truck is idleing. Sounds like a vacuum leak?
Thanks!

 

Just make the appointment and get it in that's what the warranty is for.

Best case... they fix what ever it is but does sound like a vacuum leak if new.

Worst case.. They'll hook it up to the computer tell you everything is normal and you wasted your time but it's documented.

 

That part about taking it in with no codes kinda scares me particularly with this dealer. Guess I will have to go for it but was hoping someone had seen the problem so I could go to the dealer loaded,"with information" I did disconnect some of the vacuum lines to see if the whistle would go away but no luck.
Thanks!

 

The idle in my truck varies a bit, has done it for awhile.

 

My step son has the same engine in his 2017 truck, it doesn't miss a beat. So I figured there was something wrong with my engine. The other thing which I thought was strange was the tail pipe was black with carbon,

 

My 2021 does the idle search. Sounds/ feels like a gas lawn motor when it starts to run out of gas. It is NOT loud but I can hear it . It runs fine when I put it in drive. I have 18k miles on the truck. It started about a month ago. Strange, I took a long trip out west June and July and it was not doing it when I returned. It is not due for an oil change yet but, I will definitely have them check it next time I take it in.

 

I notice sometimes a small up and back surge when I start up and start to crawl a bit. Not sure if trans related. Goes away at the next intersection.
Nothing crazy, but at almost 200K not concerned.
I started buying a no name gas, maybe that? also notice less mileage.

 

Could very well be a vacuum leak. I've seen them mess up an idle without codes and I've seen them throw codes without messing up the idle....they can be weird

A whistle is kind of a smoking gun for vacuum leak. Might involve brake boost plumbing based on where you're hearing it.

 

A vacuum leak will almost always show up as a positive fuel trim at idle. More air == more fuel needed to get a 14.7:1 ratio.
There is a tolerance of about 15%-20% until a code is set. So if LTFT +STFT is around 8-12, there could be something going on.
A bad or dirty sensor can also produce the same effect, but MAF will usually affect both banks.