I have a 2001 f150 that has 53000 miles on it. 5.4L 4x4.

After it warms up for about a minute the engine starts to vibrate at idle and at low rpms. I took it to Autozone and had them plug there analyzer in and they said I am having mis fires in cylinder 3 and 4. They suggested change the spark plugs since its at 53000 miles and it hasnt been done. I was thinking the injectors might need to be cleaned or a new fuel filter, but since its isolated to 3 and 4, I guess its probably the spark plugs.

Im not a mechanic so does anyone have any alternative solution?

How often are u supposed to change the plugs. I thought it was around 80000 to 100000???????

Thanks for the help.

 

You are having a very normal problem with the 5.4.

You most likely don't need plugs as they are usually good upto 80-100k (I have 91k on mine and the trucks runs great)

The common problem since you are showing missfire on #3 & 4 is that there is a heater hose above those two cylinders and it drips down on them and causes the coils to short.

First off check the hose way back on the pass side above the engine. It is a rubber hose that attaches to an aluminum hose and most times it comes from the factory with just a crimp type hose clamp. The clamp needs to be changed to a screw type hose clamp. If it has a screw type it needs to be loosened the rubber hose pushed further up and then really tighten the clamp.

good luck-

 

I didnt see anything leaking back by the hose clamp. I let it run for awhile too.
????????