redbond1

I've searched through and can't find a solid answer to my problem. I have a 2004 lariat 5.4 with 199,000 KMS when I'm cruising in 4th and just give it enough gas to keep my speed up it bucks and hesitates really bad. But only does it once in a while I can't make it do it on command.

I bought the truck in October 2013 and had to replace the drivers side rear O2 sensor, code went away until May and now has come back but the truck has been doing this since December. Also have a bit of rear end noise but pretty sure it just needs a brake job.

Thanks in advance!

Allinkdupp

So funny, I did a lot of searching when I went through this and didn't find much.... Here's what happened to mine (04) it started like yours then got worse, I finally got it to throw a code by really getting on it for a while.... P0300 random misfire... Long story short my truck had the wrong plugs in it... I would really start there if I was you.

truck-king80

I know the 5.4 and the 4.6 are different animals but in my 4.6 did the same thing. It turned out to be a bad boot on the coil pack. Good luck

redbond1

thanks guys I will be checking out the plugs as soon as I am brave enough and have the right tools handy just in case of breakage

Allinkdupp

My guess is you won't break any because the previous owner replaced them already with the wrong ones ...(autolite)

Allinkdupp

Checking spark on the cops is easy too, let me know if you need to know how.

Hawkins247

Had the same issue before. My fix was just a bad coil. I'd start there

Freighttshaker

My 05 was doing that I had I bad cop changed it a month latter started doing it again so I changed all plugs and cop's fpdm now it runs great

lewissa81

This is a very common symptom if misfires. Under most circumstances, the plugs are to blame. As noted though, and faulty COP can be the culprit/culprits. Until you can check out the plugs, turn the overdrive off until you reach high speeds. That normally alleviates the bucking. When you do r&r the plugs, use Motorcraft, replace the boots, clean the corrosion out of the COP, and use dielectric grease in the boots.