Engine "shudders" when given power
Here recently I have come across a problem with my 2000 F-150 Lariat 4x4 with the 5.4 liter engine. The truck has 75,000 miles on it and when I'm cruising down the highway after about a half an hour or so, when I gradually step on the gas the truck wants to "shudder", it almost feels like it is getting a lack of fuel or some type of sensor is bad and sending the wrong mixture to the intake. This only happens after the engine has been ruuning for a while and it's worse if I "jump" on the throttle and get the RPM's up and then come back down to cruising speed and accelerate again. I thought maybe the injectors are getting dirty so I tried the Lucas fuel treatment to no avail. Also, if the injectors were dirty I'd think that the engine would act up all the time or even worse when cold. I'm not getting any fault codes on the dash, no "check engine soon" light is coming on and yes the light does work, it comes on when I start the truck. So, I'm not sure if I should follow the fuel system or maybe look into the ignition system? Any thoughts????
Thank in advance for any help,
Brian in Maryland