2022 Rough Idle

[MTMan]

New member here. F150 with over 14K miles on it. Been scouring threads about rough idle but haven't run across anything definitive. You can feel it in the seat and door and even watch the tach jump and not stay perfectly still at idle. Any common issues to look for? After 3 year warranty goes out is this covered under the powertrain warranty?

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[Pigpenffx]

I noticed this too when in park and idling, it doesn’t happen all the time. What grade of gas are you using? I ran 89 through it after noticing on a hot day, 89 is mid-grade where I’m at and it smoothed it out.
Planning to switch back to 87 to see if it was the culprit or just coincidental.

 

[MTMan]

87 Octane at sea level. It's never been smooth.

 

[Tone]

Use 91. It'll go away. Went from washing machine idle with 87 to silky smooth with 91 (and 93 when towing).

 

[Pigpenffx]

Yeah, try going up to mid or high grade and see if it goes away. It worked for me-these engines can work on 87 but I don’t think they do so happily. There is a great thread in the 3.5L Ecoboost forum on here on how running different grades of gas affect the timing and ignition, worth a read as I think it is likely the issue.

Could also be bad gas if the tanks at the station have some water intrusion, but only makes sense if you fill up at the same place over and over.

 

[MTMan]

Good to know about the fuel grades. It gets Top Tier only and different stations don't make a difference. I would say the idle feels like carbureted cars back in the 80's that we're tuned lean for emissions.

 

[MTMan]

Speaking of fuel, is ethanol part of the problem?

And considering different fuel grades has anyone seen any different fuel mileage with them.

This truck has never hit 23 mpg on the highway it's rated for. 22 best mpg ever.

 

[Pigpenffx]

87 Octane at sea level. It's never been smooth.

Speaking of fuel, is ethanol part of the problem?

And considering different fuel grades has anyone seen any different fuel mileage with them.

This truck has never hit 23 mpg on the highway it's rated for. 22 best mpg ever.

Ethanol could be the issue if it sits for a long time and absorbs water from the air. Unlikely to happen in the truck tank since it’s sealed and doesn’t vent to atmosphere, gas station tank a different story especially if they haven’t been cleaned in a bit and have absorbed water or separated. But ethanol content itself is likely to cause a rough idle. Forgot to mention but if you can find e15 gas, which is usually rated at 88 octane the truck does seem to run a bit smoother and imo has better power output, no evidence to prove that just feeling, your experience may vary.

Your MPG will vary with different grades, 87 on long cruises in warm weather I’ve seen 21.6 over 1000 miles of mostly HWY driving. The higher grades will yield better, probably a 1-1.5~ MPG, but the better mileage isn’t really offset by the cost increase.

E15-88 will see about a MPG or two less due to the higher ethanol content, depending on the price it comes out even or just ahead.

I still run 87 when taking long non towing trips since the truck is at cruising speed and I don’t notice any rough running at higher RPMs and the MPGs are great for a truck. I’m guessing you could get close to 22-23 if you ran at the most economical speed (55mph) for hours, but you’ll never likely see that above 60mph. EPA numbers are a mystery, lots of ways to game those figures by the manufacturers. I’ve never seen any vehicle achieve those in the real world except at optimal conditions and even then always a MPG or two less.

 

[MTMan]

Thanks for the info. It's not flex fuel so I was assuming it was rated for no more than 10% ethanol.

 

[MTMan]

I have the factory 20" Pirellis and read that the factory Generals were lighter so guessing fuel economy is better with the latter. But, not sure I would want to try Generals as I've seen spontaneous blowouts.

 

[Ford Motor Company]

New member here. F150 with over 14K miles on it. Been scouring threads about rough idle but haven't run across anything definitive. You can feel it in the seat and door and even watch the tach jump and not stay perfectly still at idle. Any common issues to look for? After 3 year warranty goes out is this covered under the powertrain warranty?

Good morning! If you'd like to, go ahead and send us a private message with your VIN and dealer info and we’ll look into this idle concern. Thanks!

 

[MTMan]

Thank you. PM sent.

 

[Borchelt]

Assume your F-150 is not a Powerboost. The PB will increase idle when it detects the on-board inverter battery needs charging.

 

[MTMan]

Correct. It's the 3.5 EB

 

[MTMan]

Truck was returned today. Service receipt said:

"Advise vibration is normal operation as compared to multiple similarly equipped vehicles."

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