UPDATED 04 5.4 w/52k miles, 2wd, auto, never any problems like this.

I drove at highway speed about 5 minutes, slowed down significantly, say to around 20-30mph, then began to speed up again, and it felt like the truck was "missing" slightly or something similar. Stuttered maybe 3-5 times quickly then all was well.

Did not do it at all after truck came to a complete stop, but on the way back from town, each time I slowed down after going highway speed, then accelerated again, it seems like 2nd time it shifts it's sort of missing or stuttering or bumping I don't know what it is or how to explain it.

It's not a revving sound, though, like it would be if I suddenly put it in neutral, it reminds me more of driving a manual and being in too-high of a gear for your speed.

I'm worried this is something that will a) leave me & kids stranded by roadside, and/or b) cost $,$$$.$$

ETA: second 20-mile round trip, truck is definitely ONLY doing this when I'm going highway speed, then have to slow down, then speed up again. I wonder if it has something to do with the downshifting when I'm not having to downshift all the way (like it would if I came to a complete stop)?

Any insight would be appreciated, I have no idea what to do at this moment and of course I have to make one more trip today...figures huh

 

Could be a missfire, and not transmission related. That's what it sounds like anyway.... Try making the truck shudder as much as you can. If it is a missfire, then it may set a code, and tell you why.

Note: You must accelerate to 65mph and coast down to 35mph without touching the gas or the brakes to set the missfire monitor's baseline. It will not set a specific cylinder code for a missfire if you haven't done the "speed up/slow down" thing first.

 

OK, thanks for that info, I'll give it a shot in about 2 hrs during another of my endless "trips to town". I'll accelerate to 65-70 ish and let it slow down without touching gas or brake. Do I need to do this more than once?

Naturally, when the husband-person came home yesterday and drove it, he says he could not duplicate the issue...then I drove it and of course it was there.

It only seems to be present when I first obtain highway speed, then slow down, then accelerate again.

Seems to occur in the area around 50mph +/- a few, and disappears after a higher speed is obtained.

Accelerating from a complete stop does not present this issue.

The only thing we can think of to do is take it to a dealership next week. No telling how ripped off I'll get then.

I just hope I don't end up tearing whatever-it-is completely up by driving it until then. Dang it, just a few days till school starts and have to get kids things ready, you know?

 

does it occur when trying to accelerate while the torque converter is locked? if so thats misfire.

 

I have a 04' with the 3 valve engine and it is doing the same thing. Mine is occuring between third and 4th gear while under light accelleration. Most often occurs when approaching highway speeds for the first time. At first it made me think it was a transmission problem since it always happens during a shift. It really feels like a bad miss fire though. It is usually only 3 or 4 misses/jerks/shakes, then all is well. Once in a while I will be waiting for it and try to keep it missing for a bit to throw a code, but have had no luck yet. I'm going to crosspost this in the engine forum and see if anyone has any insight over there too.

 

Yep again sounds like misfire to me.

 

I'm not driving your truck, but if it shudders every time the tq converter locks, (eg. going into O/D) you probably just need to change your trans fluid. If it has been near 100,000 miles since the last time it was changed, I would try this first. Especially since its cheaper than a dealer visit, and it needs to be changed anyway.

This is a VERY VERY common issue on these Ford trucks. (we have 7 on our farm) Easily fixed. If it doesn't fix it, just post here again, and maybe somebody with some more trans knowledge can help you!

 

ok, thanks for all the info much appreciated. Kids started back to school today so now I have time to take it somewhere to get it checked out.

ETA: Sorry for the elementary questions to follow - but I don't really know what going into overdrive is for, and don't know if it's relevant but I've never touched the o/d button & never hauled anything at all, and I don't know anything about the torque converter. But wow, it would be great if I knew for certain, before I take the truck to a shop somewhere, if it's a misfire, or just needs the trans. fluid changed, or if it's something more sinister. again, thanks to those who help!

 

Got an appointment w/dealer tomorrow *sigh* guess I'll find out something then. I'm thinking you're right though, misfire. They're flushing the trans while I'm there, too. Said they'd put it on the 'puter and see if there's a code. Im guessing it's not the same kind of 'puter you get at walmart since one of those didn't get a code at all lol

 

Took my truck into the dealership, they're the only ones around here to touch these issues. Tech put it on the computer and no codes. So he drove it, felt the misfire. I don't understand how he figured it out if there was no code, but he said misfire on #1, they changed coil & plug had them flush the tranny as well. Now you can throw the pity party for me...total just for that was $413.00....to change all plugs they quoted me around $500, said for each that broke was 1hr labor....$95.00...GAWD that stinks.

Good news is that my husband, who originally did not want to risk changing the plugs himself and said "take it to the dealership", has now decided to read the info on this site, gather the correct tools, and give it a shot ;o))

Truck is running smooth as butter now, thankfully, which makes everything right with the world...everything zen, you know?

Thanks a lot guys - I wasn't quite as scared when you suggested misfire...tranny scares me, I figured that would cost a lot more $$$$