Knot Pursuit

Having a strange issue with my new truck…. Well new to me. I have used the search function with little to no success.

I am experiencing a weird bucking with the truck at very specific points. It initially felt like it may be the TPS but it is not. I will experience this issue regardless the throttle position.

What I have noticed is that when I am traveling between 45 and 55mph, with a slight load, (slight uphill) at low RPM between 1200-1700 I will get this bucking/banging. If I hit the OD off button, and do not change the position of my foot on the throttle, the issue is resolved, but the truck downshifts and my rpms climb to about 2000, and it transitions into this as smooth as silk.

Other than that I have no other issues to speak of with my truck.

The truck is an 04(square body) F-150, 5.4 4x4 auto (lariat)

Thanks guys,
Tom

mavrik2747

It's a very common problem mostly associated with a misfire, but not bad enough to throw any CEL. I had this same problem recently with the bucking and shuddering at the same points.

To solve it, change out all of your spark plugs and coils. It cost me about $170 for the COPs and plugs. This should solve your issue.

How many miles do you have on it? The bigger issue would be if the original plugs are still there, as they break easily and you will need a spark plug remover tool to get them out. Not overly difficult but painful. Lots of info on here about it.

joe mcmillan

You need to get this issue resolved soon as the misfires will damage the cats.
The bucking is most likely caused by misfires that are the result of a bad plug or COP.
As you have the 5.4, you need to read up on spark plug change procedures before you start. You should have the Lisle plug removal tool before you start. If you don't use it, return it or sell it.
Many posts available here on the 5.4 plug change procedures. Many differing conclusions as to what works the best.
If you decide to have the job done, check the shop/mechanic to find out what their past results have been. Even many Ford shops have difficulty and break the plugs. Some others have good success rates. Find someone that has had good results in the past. Don't take it to someone that has not done 5.4 plugs or has poor results.
Preparation, procedures and proper tools are the key. (maybe luck also)
Good luck
PS - Motorcraft plugs and COPS cost more but are highly preferred by most with experience.

ReaperHWK

I had the same issue. Changed the plugs to motorcraft replacements and runs like new. I did not change the COP's, I would think there is no need to as they are not consumable items. Do the plugs first, if you still have issues then possibly do the COP's.


And yeah, plug change is not easy, I would read up before you start.

Knot Pursuit

Awesome, thanks for the info!!!! I was already getting ready for the tune up/COP change out.

I will do this sooner than later.

Tom

mavrik2747

Plug change definitely isn't easy. It took me 4.5 hours to change all mine out and it was the first thing I've ever done outside of an oil change and a few other things.

It's not easy but it's very doable and you can save yourself a few hundred dollars by taking it on!

Aeromech

This may sound strange but here goes....

My 2006 4x4 Lariat has been bucking for over a year now. Just like the OP, at around 45 mph with a slight load and rpm's around 1200-1600. I've been planning on changing the plugs and insulators but haven't got around to it yet, then.....

Last week I decided to change my transfer case oil. When I did I found it had at least one quart too much fluid. This I know now has transferred from the transmission. I reserviced with the correct amount of fluid and checked the tranny. It was about a quart low.

Here's the kicker. Since then my bucking problem is either completely gone or has gotten a whole lot better.

mavrik2747

Wow that's very odd, wouldn't think that too much oil would cause that, but glad to hear you got it fixed! Maybe with new plugs and coils you can get it to go away completely.