I've searched and read every thread related, but none really seem to be the same issue I'm having.

A few weeks ago I bought a 2013 F-250 CCLB 6.2 for my company. The truck is low mileage (50k) and runs great with one exception. When driving at low throttle positions, about 1/8-1/2 throttle, it has a stumble to it that is very consistent. It's almost exactly a 2 second cycle where the engine misses slightly then picks back up and runs steady. Most of the time it's minor enough to feel, but not much to hear, but sometimes it's just right that you can even see the tachometer needle dip slightly then rise back up. There are no codes and it runs perfect above 1/2 throttle and idles just fine. I'm a mechanic, but not a Ford mechanic so I thought I'd ask and see if it's a known issue before I start trouble shooting it. FWIW< there are no codes, stored or pending, and just based on experience with brand X (my other job is irrelevant...) I went ahead and replaced the EVAP solenoid which didn't change a thing.


Thanks for any suggestions before I pull it in the shop and take up a bay of my shop to start working on it.

G

 

reset computer.

what about the throttle position sensor.? a bad spot.

I am a brand "X" mechanic. as my screen name states.

I had a small issue last year and cleaning the throttle body fixed it.

 

I should update to include that I did the reset/relearn for the throttle body (unhook battery, drain capacitors, start and idle for 15 minutes) as suggested by a ford mechanic friend and it did nothing. I'm wondering if the throttle body has a sticky spot or something to that effect. I once had a Dodge that would do the same thing with the cruise control on, when the vacuum servo would go to open the throttle a tad it'd take more force than it should have which would open the throttle too far then it'd slam shut, repeat, repeat...

I'll try pulling the TB and clean it then do the reset over again.

 

my 2013 f350 was stumbleing and throwing misfire codes about as you describe and at the low throttle response. new plugs almost fixed it completely except for a strange misfire code on cyl 8 only when the engine is cold. i did the battery disconnect with the headlights on and a jumper wire from the positive to the neg term. i don't think that i completely reset the PCM but it did help. i need to run it by the dealer and have them cause a cps relearn also.

 

I experience something similar to that sometimes. if I let the truck sit at idle or very low speeds for 5+ minutes when I get up to speed again the truck sort of bogs for a couple seconds coming going into second gear. once I get moving again it goes away...I'm thinking perhaps excessive heat soak from being at idle for a period of time. not sure if that's your problem or not but it is something similar I experience on my 16 6.2.

 

NO bog at all, just a pulsing at 1/4-1/2 throttle that varies in intensity, but is almost always present. I just pulled and cleaned the TB, letting the computer reset now so we'll see how it does in a few minutes.

Another symptom that may be connected (or not) is that a couple times since I bought the truck I would start it and when I put it in gear it dies. When that happens I have to give it full throttle for it to restart and when it does it chugs and blows a bit of smoke like it's flooded out. I've not run into this on other brands I work on.

Interesting set of quirks, even more interesting that it doesn't even have any pending codes! Mainly I have to fix this in secret so the guys at work don't give me a bunch of crap for buying a Ford and then having issues!!

Thanks for the help,
G

 

No codes at all, not even pending codes and the plugs that I pulled looked brand new still. I ran it a few hundred miles logging data and it never had a misfire. In fact the only thing that looked out of the ordinary was the throttle body graphs. The actual position and the commanded position were never quite the same and when it would start surging badly the graph looked like a hearbeat monitor with ups and downs of about 5-8% steadily. I accidentally erased the data I had logged so I'll go out and do it again here in a few.

Thanks for you help.
G

 

I had the TB in my 2016 go bad at about 10k miles. Strange surging and overall down on power. Ford replaced under warranty and it is like a new truck with lots of power.

 

G i have the same problem I have been working on, 2013 F250 supercab lb 6.2 55000 miles, no codes but the same 2 second surge, I have replaced the gas pedal which has the tps attached, plug wires, clean TB check the plug into the PCM for bent pins, no luck, i too graphed it on my autel ms908p and the only thing i can see is the throttle blade is like a heart beat changing about 6 to 7 degrees but not enough to throw a code. My truck also after setting for a couple of hours takes 3 or 4 cranking cycles to get it started, acts like it is flooded. I also have replace the evap purge solenoid on the intake behind the throttle body. I will post what i find if i can fix it. please feel free to call me and we can share notes. David

 

David, I dropped off your number and last name from my quote, but I wrote them down and can give you a call sometime and compare notes. In the meantime I'd suggest you edit your post to remove your name and number, on occasion those can lead to spam phone calls and such.

As a bit of an update, today I pulled the TB and cleaned it out, removed the gear and spun the motor a bit then put it back on so the TB control motor wouldn't be in the same place as before. I pulled the negative cable and jumped it to the positive cable to drain any/all capacitors, reset computer, etc. Then I hooked it all back up and fired it up, letting it idle for 20 minutes before I touched anything. Then I took it for a 30 mile test drive and so far it's acting like it should. The truck was never down on power, just had that weird surge. I guess we'll see if the surge stays away or comes back as the computer starts going through it's "learning" process.

Data logging on the test drive showed what may be some slight surging still, but not as bad as before and not enough to feel on the bumpy road I used. Tomorrow I'll drive towards town for 20 miles or so then head back home and see if it's any different on the smoother roads. It's definitely much better than before, maybe even cured.

One oddity I noticed while working on it, the little boot between the TB and the plenum wasn't sealed well, or I don't think it was. I know it is sealed good now. I really don't like that design, seems to give it a potential air leak right in front of the TB which will not only induce dirt into the engine, but is air not metered by the MAF which could cause running issues. I'm going to ponder on that one, but as of now I know for sure it is sealed as good as it gets so maybe that was an issue, maybe not.

I'll continue to update the status and results for any future user's benefit and hopefully we can get this figured out for HEMI392 as well.

G

 

G i too sealed the boot to the plenum not a good design but it is sealed now. I am going to pull the cover off of the tb and spin the motor and move the gear, i have not done that. will post results later today.
David

 

pics please???

 

pics of what Johnno5 if your talking about the boot, all I did was remove the rubber part from the plastic plenum and use ultra grey silicone around the boot and reinstall it and let it dry before putting it back on the throttle body.
David

 

thanks no pics needed. your description cleared it up for me. thanks again

 

Great johnno5 glad that helped, update for today, took the throttle body off again and removed the cover and rotated the motor and reinstalled the gear, put it back on, but no difference still have the 2 second cutout, I can see it on the graph of the throttle body position sensor but I do not know what is causing it. More diagnosis i guess.