Can Someone Please Help Me Figure This Out

[wweninger]

A couple of days ago while driving my 2005 6.0L I started noticing a weird jerkinking coming from somewhere. Its usually when i am on the highway at around 60MPH and i give it about half throttle. the tranny seems like it hesitates to down shift and then when it does it starts jerking but stops if i give it more throttle. The jerking its making reminds me of a carbureated vehicle running out of gas. I have checked my Tranny Fluid and Transfer case fluid and all is well. and it does it on every program setting.

could some one give me a hint on what it could be

thanks

[Vas@Diablosport]

Have you tried returning the vehicle to stock to see if the problem persists?

[PSDPlayer]

Does the vehicle have larger than stock tires on it? If so, is it an f-250? The reason I ask is that these vehicles are equiped with 3.73 rear gears and running them with larger tires like 35s or 37s leads to the truck running at rather low rpms at 60mph. When you accelerate and the computer keeps the converter locked the motor has trouble getting the truck moving. Think of it at being in 5th gear and not downshifting in a manual vehicle. A quick check to see if its the converter would be to tap the brake pedal to allow the taillights to come on. Don't hit the brakes. Just tap the pedal as you are about to step on the accerator. This will allow the converter to unlock and let the motor flare to allow the turbo to spool up.

[wweninger]

Does the vehicle have larger than stock tires on it? If so, is it an f-250? The reason I ask is that these vehicles are equiped with 3.73 rear gears and running them with larger tires like 35s or 37s leads to the truck running at rather low rpms at 60mph. When you accelerate and the computer keeps the converter locked the motor has trouble getting the truck moving. Think of it at being in 5th gear and not downshifting in a manual vehicle. A quick check to see if its the converter would be to tap the brake pedal to allow the taillights to come on. Don't hit the brakes. Just tap the pedal as you are about to step on the accerator. This will allow the converter to unlock and let the motor flare to allow the turbo to spool up.

i do have 33" tires on it and yes its a 2005 F-250 4x4. I took my friend for a ride yesterday so he could give an opinion. He also says it seems like the computer is not sure if it wans to down shift or bog down so its jumping back and forth. the thing that confuses me is that ive had 33" tires on my truck since i bought it in 05, this just became a problem 2 weeks ago... wouldnt it have done it all along???

[muckymudder]

You could have several diffrerent problems. First could be that as already stated your truck is having torque convertor problems, second you may have a faulty egr valve (just had a truck in with the same problem, replaced the egr valve which was stuck open allowing too much air in which in turned caused the bucking) or you may actually have a tranny problem. My guess is probably the egr valve since we seem to see this happen most often ( I was a Master Ford Tech till 2 years ago but still do work on diesels at home for certain customers & am now a Service Manager at the local Ford garage). You'd be best to bring in in to a Ford garage & get them to diag the issue.

[thomas5853]

I have a 2003 6.0 and noticed that when I changed my tune while towing, my truck started the bucking and a puff of black smoke shout out the back. But then I pulled over shut it off, added some cetane booster, and then I was fine. Later on on the road trip, i changed the tune and this time I started it and then shut it off before continuing on the trip. It started to act up again, even though I added some cetane booster. So I stopped and it only happened a few more times. Maybe my egr valve needs replacing? I thought I had gotten bad gas? Anyone with another idea?

[PSDPlayer]

If the EGR valve was opening, he would have mentioned that the boost gauge would have been fluttering between 8-12psi. If the turbo was stuck at a certain point and was over boosting and blowing the EGR valve open from boost pressure being higher than the exhaust drive pressure, codes would have been set. One code for exhaust drive pressure not responding to the PCM requests and an EGR system code from the valve opening when it wasn't supposed to.

I did not say he was having converter problems. I said, due to the normal strategy of locking the converter in overdrive at low throttle points and the newer Ford calibrations requiring more than a 50% tip in to release the converter, he should try taping the brake pedal to feel the converter unlock.

[muckymudder]

Just had a truck in the shop here with the exact same issue. Customer had the truck at various other shops trying to diag the problem but nothing ever found. I road tested with the customer monitoring the engine with our scan tool & noticed that the #5 injector was missing intermittently causing it to buck & jerk. I'd recommend taking it to a ford garage & road test with the tech & monitor the power balance to see if you may have a faulty fuel injector.