2001 F150 155,000 miles -have only done regular maintenance and changed the plugs 5 months ago. Lately upon acceleration-getting on the highway, etc. and then coasting to merge ,getting close to traffic etc. & then accelerating again the truck will start to buck & miss. Yes the check engine light is on- o2 sensors-but it has been on for over a year & it always ran fine.
Any ideas?
Thanks

 

What you are experiencing is a low RPM, high load miss in one or more cylinders.

When the plugs were changed, did you use Motorcraft plugs? Did you replace the COP boots at that time? Did you use any dielectric grease on the COP boots?

Good luck!

 

Get it hooked up to a computer a would bet it is probably a coil.

 

my truck is the small v6. i think it only has the coil pack. i am planing on getting it over to abe diagnosed-just wanted to have ammunition so i know what i'm talking about when they tell me what's wrong.could 1 coil be doing this? thanks, chuck

 

Could be the coil or the spark plug wires. Have the wires been replaced? Motorcraft?

 

No..I didn't do that-replace the wires. Guess they could be breaking down on load........I just thought it would run rough at more times besides just acceleration after acceleration.& gotta tell ya, thanks for responding.
Chuck, San Jose,Ca.

 

let us know what it was. i'm curios to know.

 

It is highly possible that the plug wires are indeed wearing out. They really should have been changed at the same time that you changed the plugs.

When you're accelerating you are placing an increased load on the spark plugs. Naturally, that electrical load is supplied by the plug wires. So, it is reasonable to assume that one, or more, of them could be wearing out to the point of total failure soon.

You mentioned that you have done "regular" maintenance on your truck. Does this include the fuel filter?

When accelerating you are placing an increased demand for more fuel. If the fuel filter is becoming clogged then your increased demand will be met with resistance. The truck might run perfectly fine when the fuel demand is low (coasting, driving at low speeds, etc).

But, when you try to accelerate, the fuel can't pass through the filter quick enough. And, you will get the symptons that you have described.

 

Stock coils do tend to break down under a load(acceleration), especially if it is "on the blink."

Ford Truck V6

 

Had the same problem with mine. I pulled the codes miss fire on multiple cyclindrs. It ended up being my coil pack. Pretty easy to replace and inexpensive. I think I paid 70 bucks for it.

 

I have a 2000 f 150 5.4 bi fuel with 75,000 miles on it that use to buck like that on both gasoline and cng.Had the filters changed no difference.Had the plugs and one coil replaced and now it runs great on gasoline and better on cng but it still bucks every now and again only on cng around 45 to 70 when I let off the accelerator and then go to give it more gas. Sounds like a similar occurence only different fuel.The plugs and coil fixed the problem with gasoline and We are still trying to figure out why it is doing it on cng.We think it might be the high pressure regulator.$800.00 bucks to check that theory,ouch.

 

I have a 2001 F150 and my truck is doing the buck amd miss when accelerate . I do not have a check engine light and it has been doing it for about 4 months? What could it be? Could it just be a bad spark plug??? Have not replaced since I've owned at 63,000 and now it's at 93,000. I have had three coil packs replaced but check engine light came on when that happened and it was a lot worse

 

as you said, it has to be "worse" to get the light. yes you can have a spark plug or coil problem that does nto miss continuously and it will "miss", but not set a code. sometimes if you tromp the throttle, then slow down, then tromp, etc with several hard accelerations, you can get a code.

 

Another question I was told that my rear-end is probably going out? What are the signs? It's not clunking when I put it in drive or reverse?? I am going on a six hour drive to Idaho???

 

My 2001 4.6 F150 also misses when accelerating. Not hard acceleration, but "nominal" acceleration, like going uphill. No check engine light. The spark plugs were checked (good), fuel filter replaced, and #1 cylinder coil replaced. Problem persists. Should I check plug wires next?