Hesitation/Bucking @ 45 MPH under very light acceleration

[1997SCEBFEX]

agree w/flush, filter, & fill trans. would also do the rear diff as well, and if she's a posi (lim slip) ensure you add the friction modifier. I trailered heavily my first few years, thus changed the trans filter & fluid every 25K.

Other things mentioned, but perhaps still a second look:
*driveshaft balancing; did anything recently come in contact w/it or one of the weights (if you have them) perhaps come off?
*Throttle position sensor? Took mine approx 14 months to set the code and I thought it was the tranny the whole time.
*Vacuum leak(s).
*Wheel weights? Have you had recent service, new tires, &/or balancing?
*Lastly, an emerg brake shoe(s) dragging?

Hope you figure it out & let us know your resolve.
Best,
PanHandler.

 

[skipppy75]

The dealer 2 miles from me wants to do the update firmware TSB for under 10MPH stop issue and start acceleration issue from a stop for $140 and said they don't know if it will fix the 40-60 mph issue and they need the truck for at least 24 hours since they are so busy lalalala and then they want to charge me $89 for a guy to sit in the truck with a laptop to trouble shoot the 40-60 MPH issue, I have told them to go stick it where the sun don't shine. I left that place disgusted so I finally got on the phone for a 3rd time with the dealer 1 hour away I bought the truck from and found a salemen willing to tell me this is a known issue for the shuttering issue to occur when lightly accelerating when your between 40-60 mph and he thinks they have a fix.
I am waiting on a call back from him to hopefully set something up for Monday because service manager is out today to have them check it out. I will definetly respond here on what they say they need to do and how much it is gonna cost me.

 

[2007EXPY]

Same issue uphill hesitation, pinging knocking at 2.5 to 3K rev range; I also get a loud clunk when lifting pedal at speed-60 to 70K.
No problems surging or lurchinh forward at a stop.

Changed plugs moderately improved performance but still get the knocking pinging.
Changed out 3 COPS some weeks ago as those plugs were misfiring may... replace them all but I do not think that is the problem.

I have run some engine cleaners fuel additives, yet with my CEL light coming on under acceleration, when the engine is misfiring, I think it is just fouling things up again.
I am going to try the Berryman spray which get atomized via the air intake, to see if this improves anything.

Changing Tranny filter and dropping pan only replaces about half of the transmission fluid.
If 7 quarts makes a difference Im curious how much an improvement removing all 14 or so would have. I may just drop the pan as this is service I can handle and it is more affordable than going to a dealer to repalce all.

I may next consider replacing my catalytic converters as with the enigne misfiring , the raw fuel being exhausted may have damaged the units.

Not sure what my next step would be.

 

[2007EXPY]

Curious how other have made out.

 

[metaldrgn]

One of your coil packs might be bad. Do a lawn mower check or use a multimeter to check resistance (open or short bad, don't know spec. resistance but check many and one out likely the bad one.

Don't get caught in belt or get bit if doing the lawn mower check.

That check won't work as his vehicle is missing under load.

 

[metaldrgn]

Do you feel hesitation/misfiring under heavier/WOT at those speeds? If the knocking gets worse don't push it too much or it can destroy your engine.

You can do a tranny flush yourself if you want. It can be difficult because you pour the new fluid in as the old comes out. Plenty of videos on YouTube. I did it myself with no problem. Even with a flush you'll still have some residual in the transmission but it'll be a lot less than a pan drop only. I wouldn't recommend this if this is your only vehicle or if not having it would cause problems.

 

[hancock1228]

Skippy75 - Did you ever get this fixed? My 2005 (150k miles) is doing the same thing - miss/hesitation when slightly accelerating at 40-45 MPH.

 

[f150dave2002]

I'm hunting the same problem in my 2007 Exy with 97k miles. I've replaced coil packs, #7 & 3 that showed a miss on my scan gauge2. So far still has the problem.

 

[case2001]

I don't know if this will help but in my 1999 (I read the thread I know it's not a 99 with the problem). I had same issue. I refused to keep on changing things until I had a bigger problem. Went on for 15000 to 20000 miles only in speed described and with similar valve clatter. It was the EGR controller. Replace it and the truck is still smooth as silk 80,000 miles later.


Sent from my iPhone using Tapatalk

 

[keisha]

I have the same problem on my 08 limited and what helped me out alot but not completely fix the problem was a tuner. I have the cortez superchips tuned with the 87 octane program and seem to help about 60% of the problem. It now only stutters/ hesitate once in a while and its not as drastic if you know what I mean