I'm having a problem on my '04 5.4 with the engine surging when going down a hill with the cruise control on. It feels like you're pressing on the gas and letting off all the way down the hill. Sometimes it's so bad the driveline clunks. On a really steep hill, the speed will actually drop up to 5 mph below the setpoint before the bottom of the hill and then the cruise will kick in and bring the speed back up when you start up the next hill. Drives me crazy! I had it looked at by the dealer today and of course, they couldn't replicate the problem so all they did was update the software and that did nothing. There's no way they actually drove the truck down a hill with the cruise on not to have noticed the problem. Have to take it back next week to have the rear window replaced so I thought I might be able to take a little ammo with me when I go back. Anyone had this problem and had it fixed??

 

I too have an '04 and have noticed the same thing. What I notice is one time the truck will act like it's coasting and will actually over run the cruise set speed. Most times it will maintain cruise set speed with the occasional surge. I haven't had the driveline clunk yet, although I do remember it clunking when towing our camper, as if the LS clutch pack in the rearend was slipping. The dam thing better break before my extended warranty runs out.

 

I think I fixed this one myself. The dealer couldn't replicate the problem (no way they drove it with cruise on down a hill!) and just reflashed the computer. Of course, this did nothing .

The problem turned out to be a dirty (sticky) throttle body. When going down a hill, the CC would try to give it a little throttle and the throttle plate would stick shut. It would throw in a little more power to the stepper motor and the plate would come unstuck and overshoot with too much throttle. I cleaned the throttle body with a coating safe cleaner and no more problem! I only live about 3 miles from work so the engine hardly gets to temp before its shut down. That probably has a lot to do with the excessive soot in the throttle body. My '97 F150 had a sticky throttle plate once and that's what made me think of it. Hope this helps.

 

Very interesting...never heard of a throttle plate sticking after only a few years....

Also, I'm pretty sure there's a TPS in the throttle body, which should tell the computer the thing is sticking! I thought that kind of thing would throw a code!

 

Yeah, my service manual says the tps gives 2 position feedbacks to the computer, one positive slope and one negative. Since there were no codes set, I figured the problem must be mechanical in nature. I guess since the throttle plate didn't stick permanently but just for an instant, it didn't set a code. The plate sticking explains why it only happend on a downslope where there was only a small amount of throttle needed to keep the set speed. It would also surge when going up the ramp in the parking garage at work when I gave it just a little throttle.

My '97 with the 5.4 starting sticking at about the same time, about 3 years old. You could feel it sticking in the pedal and couldn't start off without a jerk...