1999 Ford E 150 Hesitating

I’m having trouble with my van. It has a 4.6 v-8. It started having a problem hesitating. I had it checked out by my mechanic. I replaced the fuel filter and he checked the fuel pump presseure and its fine. He checked many other items as well and came up with nothing. There is no check engine light on. We both are starting to think it may be a transmission problem. The problem is similer the the experience that when the transmission is in overdrive and traveling at low speeds and it sputters.Its not that because I have the electronic overdrive in the off position. It happens a lot when I am accelerating uphill.

Any help is appreciated.

The problem might be caused by carbon deposits formed on the backside of the intake valves. If enough of this carbon has built up, it can restrict the proper flow of air and fuel from entering the cylinders. And if severe enough can act as sponge and absorb some of the fuel that’s suppost enter the cylinders. So you might try a decarbonization of the engine.

This can be done with a can of SeaFoam Motor Treatment. Get the engine up to operating temperature and shut it off. Disconnect the brake booster vacuum hose from the brake booster. Adapt a smaller hose that will fit inside the brake booster hose and into the can of SeaFoam. Pinch off this smaller hose with a pair of pliers. Have someone start the engine and bring the idle speed up to 2,000 RPM’s. Slowly open the pliers so that the SeaFoam begins to be drawn into the engine. It’s here where the throttle must be manipulated and the pliers are opened and closed to meter the SeaFoam so that the engine doesn’t stall. Once all the SeaFoam has drawn into the engine, shut the engine off and let it sit for a half hour. Reconnect the brake booster hose. Restart the engine and bring the RPM’s back up to 2,000 RPM’s until the smoke out the exhaust disappears.