Hey guys, I have an 04 Ford F150 with the 5.4L 3v. I have recently started having an issue with the truck feeling like it is slipping. It does it through all speeds, and it does it between 1200 RPM and 2200 RPM. Usually under a load. It also won't do it until it gets good and hot; after 20 min of driving. It won't do it with the overdrive off.
I was having the issue with the truck bucking under a load between 45mph and 55mph about 8,000 miles ago. SO I replaced my overdive servo and retaining clip. Cleaned up the valve body and replaced filter and fluids. That didn't fix it, so I replaced all 8 plugs. That fixed the problem. Now, 8,000 miles later it started doing something similar. So I thought automatically that it was my coil packs, since it doesn't do it until it heats up. I replaced all 8 and it is still doing the same thing.
Do any of you have any idea what could be going wrong? I appreciate any help I can get. Thanks

 

So mine has been doing this for about 3 months, same speed and RPM as you and only when I try to accelerate a little bit without it downshifting. It kicks rapidly when I give it gas. Doesn't do it from a start, when it downshifts, or at higher RPMs. I have been looking into having my transmission serviced thinking it was most likely the problem even though my fluid is clean (my pan leaks and needs a new seal but fluid level is still good).

You said you changed your plugs and that solved it for a bit? It's been a while since I did mine, maybe that could be it. I have no codes showing when I run a check so I didn't think about the plugs or coils.

 

After reading your post again on my way home from work I tried turning overdrive off. I couldn't get it to do it with it off. Turned it back on and couldn't get it to do it again with it on. Hmm might be a problem with that? More troubleshooting I guess.

 

Yours definitely sounds like a spark plug or coil pack. Mine may end up being that. Im going to mess with it this weekend.

 

I ordered up a set of plugs and a Lisle tool. My plugs have been done before and they are probably due. I cant see if a coil is bad so I'll wait on those, don't have $800 at the moment. I'm still questioning the transmission but change plugs and see if I notice a difference.

 

Put a tank of 93 in and switched to my performance tune and it won't do the kick/stutter at all. Just got my set of plugs in the mail today, waiting for my lisle tool to show up before I tackle it.

 

Ive got the same issue. only when tranny get above 140 degrees usually if im coasting around 45mph and give it some gas to get up to 50 it will slip. Tranny only has 10,000 miles on it. Can one of you explain why plugs and coil packs would have anything to do with that?

 

Is it slipping or stuttering? Stuttering is low grade misfire.

 

Stutter is probably a more accurate description. Changing the plugs this weekend

 

Mine is a stutter, like someone is under the truck kicking the transmission with both feet.

 

I would call mine more of a shutter now. It has gotten worse and now will do it after about 15 minutes of driving. I have replaced plugs again and coil packs. I also added "shutter fix". I just recently changed the tranny fluid and filter about 10,000 miles ago. I feel mine from about 35mph and up. It feels like I'm running over a cattle guard. I guess I'm getting ready to replace the torque converter now. Does anyone know the stock stall on my tranny?

 

When I dont feel the shutter, it feels like it is going into neutral for split second. It only does it around 2000 rpm. And its not until a little bit into my drive does it do this. I think I can rule out ignition problems.

 

Have you tried running premium? I've been running it and my truck rarely does it now.

 

Yes, I actually did that and I cleaned my MAF sensor yesterday. Neither helped.

 

I changed my plugs last night as my first step to fix this problem. Well on my drive home with my custom tunes taken out and the truck returned to stock my stutter was gone! I couldn't get it to do it once! I still have 1/4 tank of 93 in it so when that runs out I'll put 87 back in and see if that makes a difference. Some of my plugs were definitely worn out.



Here is a used vs new:


It would also appear I may have some buildup in some of the cylinders.