It is not the Fuel Filter

Hi, I have a 1998 Ford Expedition 5.4 with about 198000 miles. About two days ago it started acting like it was not getting fuel, or the brake was stuck on. Checked the fluids oil was a little low but nothing to write home about. My husband changed the fuel filter but that has not helped. It seems to get worse when the engine warms (around 30 minutes) up and is worse when I am at a stop light or between 50-60mph. Any ideas?

So you’re at a stop light. Then what happens when you hit the gas pedal? Does the engine rev but the car doesn’t accelerate? Or does the engine stumble?

The engine stumbles like it is not receiving enough gas to engage the engine completely. It moves forward but just not like it should.

I should add that when it is in park it idles very rough as well, the warmer it get the rougher it idles. I does not however overheat, it stays within the normal range.

Does the check engine light come on?

Has the iac and maf been cleaned? When was the last time it was tuned up?

Is it a consistent miss, as in the same cylinder missing, or is a intermittent, like random cylinder misses?
I’ve have the 5.4 coils act right when they were tested on an ohm meter, or when they are cold, but once they warm up, they show their true colors and start misfiring.

Does that sound right to anyone else? A coil-on-plug failing?

Those coil packs can apparently fail due to excessive spark plug gap. If you haven’t had the spark plugs replaced at recommended intervals, the gaps may have become excessive and may be starting to cause the coil pack(s) to fail.

I would start by replacing the spark plugs if old/worn. Then if the problem persists, check the coils. If it keeps stumbling, the check engine light may come on. When it does, there will be a “code” set inside the computer. An auto parts store can read the code for free and tell you what it means.