2006 Ford F150 5.4 engine cuts out under medium acceleration

My truck has about 100,000mi and has had all the scheduled maintenance.

My 2006 5.4 engine cuts out under medium acceleration when accelerating from a stop. Happens when warm or cold. Works fine under light acceleration. Cut out happens before it shifts into second. Cuts out just for a second, then resumes. Stumbles twice under heavy acceleration. Very repeatable.

I noticed the gas was low - above E but below 1/4. So I filled up at the gas station. The problem went away. I had this issue with a 1980s fuel injected VW - it would get a vacuum lock on the gas tank. But with this truck I did not notice and inrush of air when I took the gas cap off.

I suppose it could be the gasoline sloshing towards the rear of the tank, away from the fuel inlet pickup.

Anyone know these trucks well enough to know what the actual problem was?

It sounds like it happened only once, except you seem to also describe it as an ongoing thing. Hard to tell.

You probably want to have your fuel pressure checked out under load. You can get this from a marginal fuel pump. With lots of gas it keeps up because it gets help from the head pressure - literally the weight of the gasoline. Once the gas is low its weakness shows. If you manage to get the pressure checked do not just allow someone to do a simple check of static pressure. You need to see how well it keeps up under load.

Sometimes when people say “has had all scheduled maintenance” they mean oil changes. So you might also mention some specifics re: things like plugs & wires & filters.

Has all scheduled maintenance as per the user manual - done by the dealership. So not just oil changes. Plugs when required, filters, brakes, etc. etc.

Happened for one day only, until I filled the tank.

Fuel pump eh?

I think it is a defective spark plug coil. I had the same exact problem on my 2003 F-150 with the 5.4 engine.

I’m with Cigroller on this 100%.

Just as an FYI, gas tanks, oil pans, and other mobiile fluid tanks have “baffles” inside to prevent the movement of fluids from affecting operation. “Sloshing” is not the mroblem.

Have fuel pressure checked, replace fuel filter. Have you changed the spark plugs yet? It’s time…