I have a 2001 Excursion, 185k miles. Last week I started it in the morning....not cold out...and it started fine and ran fine. I begin to move it and it was like a switch cut on and it began running very pooly....like it would if it were 10 degrees out and you didn't plug it in, or if the fuel filter was bad. Very rattly and no response when pressing the gas pedal. It did this for a couple minutes so I shut it off. That evening I turned it on again. For about 2 seconds it seemed fine, then it immediately began running rough again for about 2 minutes. Then it ran fine. I actually drove it about 15 miles to a service station. I had scheduled to get 4 glow plugs replaced. I told them about the problem and asked them to check it. They replaced the plugs and test drove it and said it was fine. I went to pick it up this morning. I turned it on and it was fine for about 5 seconds then immediately started running rough again. Did that for 10 seconds then ran fine. It's like a switch is going off/on...runs fine then runs rough then runs fine. Does anyone know what this indicates? Clogged jet? Fuel pump? Fuel filter (only 1 month old)?