I have a 2016 F-150 SCREW with the 3.5 Ecoboost. It has ~27,000 miles on it.

In the last 5 thousand miles or so the truck has developed what I would describe as a 'stumble' at idle. It's enough that I can definitely feel it just sitting in the truck - in the seat, steering, floorboard, pedals.

If you get out and open the door and watch the edge of the door you can see it visibly shake up/down by maybe 1/4 to 1/2" and this is once every 2 to 5 seconds or so. Between the stumbles it feels like it runs fine.

When driving down the road I've noticed no issues - it seems to drive just fine / have power / etc.

When I'm coming to a stop I can almost feel it start to stumble and once at a complete stop I can feel it for a few seconds before it smooths out for a few, then stumbles again.

Honestly it just feels like it's idling lower than it should. I can visibly see the RPM needle on the dash move - albeit extremely slightly - when it does stumble - and it's idling just a *hair* above 500 RPM.

In the past with older vehicles I've seen this behavior when the A/C would kick in - the RPM would drop, the engine would stumble for a second, and then it would stop stumbling. I've turned off climate control entirely and the issue persists.

I went by my local dealership and they told me to try premium gas. This engine, as far as I understand it, was designed to run on 87 so switching to a harder-to-ignite fuel shouldn't help with an idle issue afaik.

I did try it just to rule it out - and it behaves exactly the same on premium as it does regular.

I've changed the oil every 5,000 miles with Mobil 1 synthetic since it was new - the first change at 1,000 miles.

The dealership is telling me that without a check engine light there's literally nothing they can do. They've gone so far as to say this is 'normal'.

Any advise / suggestions on what to check / what to do / what to say to the dealership would be appreciated. It definitely doesn't *feel* normal to me.

I can't think of anything that would cause this that I could swap. I did think about changing the spark plugs just to see - but if it were the plugs wouldn't I have issues while driving as well and not just coming down to an idle / at idle?

Sorry for the long-winded post. I'm just really not sure what to do. It idles rough enough / stumbles rough enough that sitting still I want to shut the truck off to stop the vibration / shaking.

Any and all help / advice is very much appreciated.

 

Possibly a cam/crank position sensor going bad (intermittent)? Might not set a code, but the dealer can watch the datastream from all sensors if they really wanted to.
Are you at the dealer you bought the truck from?

 

The dealer I bought the truck from is a huge PITA to deal with.

It is my local / close dealer.

They will plug it in and watch it if I ask them to - but I generally have to know what to ask for. It definitely doesn't feel normal. If I were to test-drive this truck to buy it used - I'd take a pass on it due to this.

It does this all the time - but it's off, on, off, on. Stumble for 2 seconds, run smooth for 3, stumble for 3 run smooth for 5, stumble for 3, run smooth for 3. I do notice it *every* time I come to a stop though. It's like the idle is dropping too low and then it's having to come back up.

 

Normally I would recommend working with the selling dealer. They have just a little more skin in the game.

 

OP...you might be experiencing Direct Injection Carbon Buildup on your GDI Ecoboost.

Take a look at these utube videos for more info...







biz

 

They damaged my truck [body work] with less than 1k on the odometer and then blamed me for it. It's too bad for them I do a video walk-around of my vehicles before I drop them off and when I pick them up [I've had **** like this happen before, apparently I have bad luck].

I had to have my own PDR guy fix it and then I had to fight to get reimbursed.

They filed a claim on my warranty saying the truck was dead and they had to come out, tow it, replace the battery, and some other stuff - to cover the $$$ they paid me to repair the body work damage.

Let's just say that that dealership and I are not on 'speaking terms'.

 

I was aware of the GDI Carbon Buildup on valves - but didn't really think that was an issue until ~100k+ miles.

That said - I'll look at the videos because from the thumbnails it looks like there's something I can do about it short of pulling the heads.

 

Oh...at 100k+ miles you'd certainly have to pull the heads. At the current mileage...using the CRC...might just do the trick.

Good luck with it.


biz

 

I'll do it and see if it helps.

 

A few questions:
1) Are you running a tune or any performance mods?
2) Do you do a lot of city driving?

Everyone seems to agree these engines are hard on spark plugs and changing them at 50K miles is a good idea. If you're running a tune, then 30k miles is probably better. These engines like to be run, so slow, city driving I feel can add to the carbon issues. If you haven't run the engine hard lately, go play in Sport mode down the freeway and see if the engine runs better afterwards. FordTechMakoLoco will say these engines like this kind of "Italian Tune-up" occasionally.

I'd start with a fun run in Sport mode and then change the plugs. Cheap and easy way to either solve the problem (hopefully) or eliminate it as a possibility.

 

Is this an approved process by Ford? Ford has been working on a solution and I hadn't heard they've released an authorized process. Many don't recommend these non-authorized methods as they can cause more damage.

 

100% Stock.
Not really - I live in the country - there isn't really any stopping between me and where I'm going.

I drive the thing like it's stolen constantly. I love this truck - just not it's stumbly idle.

Going to gap the new plugs to 0.28 and swap them in and see what happens. Will also inspect the old ones when I pull them out.

 

Cool...post back here how they look and if that solves the problem. It's always good to have that reference info here for the next user.

 

I definitely will. There's nothing worse than somebody posting up the same issue you have - and then never hearing what came of it. Was hoping to change the plugs tonight but it started pouring and I don't have any cover so I'm doing it tomorrow.

 

Has your fuel mileage changed significantly?

My 13 would idle rough.
New plugs would help for a little while.
I just learned to live with it.

I had 147k on it when I traded it.
No valve issues.... ever.