Space Cowboy

I have a 2004 Ford F-150 with 5.4L. When I accelerate down the road, it does fine until I hit 45 MPH, then it stutter with the shifting. If I increase the RPM’s, the stutter goes away. It will not do this at any other speed, just at 42-47 mph. I have had the firmware updated, plugs replaced, tran oil changed, no changed. Any suggestions?

Justin77

What did you update the firmware on and how did you do it?

dos0711

Bet it goes away with overdrive turned off...

lewissa81

^^^ What he said.
When you replaced the plugs, what kind did you use? Did you replace the boots and clean the cop contacts? The 45 mph jerking/stutter/bucking is a common misfire indication and doesn't happen when O/D is off.

wolfy53

exactly what lew said above i would bet money its your spark plugs.

Mine did this during the test drive. 98k miles original plugs. I made the dealer change them as part of the deal. The miss or shutter went right away.

When I saw the plugs, the gap was huge compared to new plugs. Like 4-5 times larger. No wonder there was a problem.

hauptbuilder

Hey, thanks. I just now registered to this forum for exactly that issue with my truck, and in 2 minutes I had my answer. Thanks again.

Justin77

Spacecowboy said in his post he had already changed the spark plugs and it still stutters

wolfy53

You are right. Sorry I was on my phone last night and missed that. Thanks!

lewissa81

New parts aren't always perfect. Any sparkplug can develop tiny cracks in the porcelain that allows arcing, or may just simply be defactive. Misfires aren't only caused by sparkplugs. I'm not saying that this is the definitive cause for the stumbling, but it wouldn't be wise to ignore the plugs just because they were changed with an unknown brand/quality. There are many tales about people having the same, if not worse, problems after installing non-Motorcraft plugs.

zapperman

I had the exact problem at 90k and it was not the plugs or cops, it was the torque converter shudder. 2 bottles of Dr. Tranny shudder fix and it has not done it again for 30k miles.