This is my first post, so I hope I don't sound like a complete idiot. I own a 1997 F-150 4X4 Lariot, 5.4L with 153,000 miles. I have been very diligent with the service of the truck.

Last Thursday on my way to work, the truck started to shudder/buck when I went to pass someone on the interstate. I have never had any problems with the transmission, and I'm beggining to wonder if it is finally time for it to give up the ghost. It's been about 40,000 miles since I had the transmission fluid changed (I had the fluid flushed through the transmission lines).

When I accelerate slowly and smoothly, there is nothing wrong, but the minute I try to accelerate quickly, it does this.

I have been planning to change out the U-joints (front and back driveshafts) Tuesday evening, even before this started. I guess I have even more reason to do so now, hoping this will fix the problem.

I have read through other posts where people had talked about torque converter shudder, and I was wondering if this is what they were talking about. But this is not a slight shudder. My fiancee says it feels like the frame is about to shake itself out from under the truck.

Thanks in advance for any advice.

 

Hi and welcome to the forum

No you don't sound like an idiot. Your question is a lot easier to understand than some
How many miles on the spark plugs? Fuel filter?
To me what you're describing sounds like a misfire, probably caused by a bad spark plug.

 

Thanks for the reply.

As a matter of fact, I downloaded and printed your directions for changing out the sparkplugs last week. I am ashamed to say, that I have about 150,000 miles on the plugs. I just don't have the money to have them changed out and am a little intimidated by doing it myself. There is a lot of "stuff" around those plugs that I'm afraid I will mess up. I just guess I have to bite the bullet and dive into it myself. I changed the fuel filter 2 months ago.

Why would I detect the misfire only on harder acceleration? Weak spark? When I accelerate very slowly and smoothly, this doesn't happen.

Thanks again for the help.

 

You're welcome

Under more load, such as a hard acceleration, it's harder to fire the spark plugs so there is more chance of a misfire. With that many miles on the plugs the gap will probably be quite large and that takes more energy for the spark to jump. Unfortunately that can be hard on the COPs too. Hopefully you don't have any bad COPs but the spark plugs are where you should start.
Let us know how it goes.

 

My future father-in-law and I looked at the spark plugs on my truck last night and tried to devise a plan into changing them out this weekend. The instructions you posted will be a great help, but I have to ask, how in the heck do you get to the back sparkplug on the passenger side of the truck. I can barely see it through all of the hoses, much less get my hand on it.

Also, is there anyway to check the COPs in case one of them has gone bad? Maybe with a multimeter? I would like to check them while I'm changing the plugs.

Thanks again for the help.

 

The back one is pretty hard to see but once you start working on it it's not so bad. Move the heater hose out of the way and maybe the PCV hose. You don't have to disconnect the heater hose. It will move out of the way quite easily.

 

Old plugs can cause these symptoms big time - you might also consider new plug wires.

 

Yesterday, I finally changed the spark plugs. After 6 hours of work and then trying to track down the source of an air leak (the PCV hose was pulled loose trying to get to cylinder #4), the misfire problem has gone away. Needless to say, after 150K miles, the old spark plugs were not in the best of shape. The smallest gap was 0.072 and the largest was 0.083.

Everything went well on the sparkplug change, but as everyone says, the back cylinder on the passenger side is absolutely no fun. I would say that I spent 2 hours labor just getting at that one plug. My hands look like I've been playing with a porcipine. Anyway.

Racerguy, I just wanted to thank you for your help. Your instructions made the job a lot easier and saved me a ton of money.

 

You're welcome
Good to hear that you got it fixed.