All, i have an issue ( or at least i think its an issue) with my 99 f150 5.4. When i use my cruise control, i notice when i put on the brakes slightly to slow down, it feels like its not coasting because you can feel the engine still engaged and wont coast. I think this happens even without the cruise on. Does anyone have an idea on what this could be? I have the latest update on the cruise control harness. I believe that was for power always to it even in off, causing fires. Help?

 

If you feel the motor still pulling after the application of the brakes, that is a very unusual situation.
Are you sure?
Because there is a DUAL knock-off of the CC system so this cannot happen.
1. The pressure switch on the master cylinder opens power to the CC system when very low pressure is detected.
2. The brake pedal switch APPLIES power to the CC system as an 'inhibit' signal.
3. Under a certain low road speed the CC will fall out by itself.
You must be sure the CC is responsible for the motor still pulling the truck.
Check for a stuck throttle cable between the CC and the throttle body or anything that prevents return to idle.
The only other source is the transmission converter has a one way lock mechanism.
If this does not release, the motor will power the truck just from that lockup fault when it should release as well.
Be sure the CC is off and make a test drive.
If you still feel the drag it's not the CC.
Good luck.

 

Or extra air is being drawn in through an air leak or a wonkey IAC valve. Is your idle speed in specs?

 

I do have a weird acting idle and the first thing i suspected was my IAc, it was under lifetime warranty so why not change it. Also, i just changed the entire heated PCV hose and lines from the rear of the intake manifold fwd. All the other vacuum lines look descent, thats why i started looking into coil packs. It always idled well, even in drive, but recently it just started shaking in drive and can kind of hear a little miss out of the exhaust. I have an obdII scanner, but it isnt very sophisticated. Mostly reads codes and gives me some live data, but nothing to do with cylinders, o2 sensor voltage, iat temp, idle speed, vehicle speed, a few minor other things. I did change 3 coil packs, it got half better (itll have normal idle, then rough, normal then rough, i think im on the right track, already changed all the plugs. Btw, it drives great. Good pick up, and so on. Bluegrass, i forgot to mention that my cruise control will keep it at the designated speed, unless your going downhill, then it doesnt seem to work, i always have to slow down and reset. Kind of contradicts what i was saying about it earlier, but it does both the issues i stated. I feel the engine pull back on level ground, after disengaging the CC and it doesnt maintain speed downhill.