my truck is a 2004 4.6 4x4 with 97,000 miles. ever since i got it when you driving around 35-55 or so about 1/8 throtle i can feel a slight surge. it feels like the truck bucking at little bit. i just replaced the plugs about 500 miles ago and the did nothing but fix my rough start up. i didnt replace the COP's i dont know if this is a symptom of bad COP's? also in park when you rev it to about 2000 rpm and let off it will drop to about 300 rps lower than idle and catch itself. when it does this the lights will slightly dim. the battery is stock and 6 years old. could this be the problem? im stumped and i would really like to figure out what is causing this. today im going to get a new pcv valve and see if that changes anything. any help would be greatly appricated. thanks

 

Try cleaning the throttle body

 

I believe this may be two separate issues. I say go ahead and change out the battery, it may fix the dimming lights issue, and it will be a good preventative measure before you find yourself stranded with a dead battery.

As for the surge, I suggest cleaning the MAF. Others may have more info.

 

i have already cleaned the TB and the MAF. i did the "gotts" intake and my exhaust is just straight after the cats and dumps right after the cab (its a regular cab). could be something with not enough back pressure? i can also fell a "bump" when i let off and hit the pedal anytime over 40 when it is in overdrive. it feels like its the ring and pinion and has slack in it or something but if i did i would think it would be at all speed. i can put it in second and it wont do it at all and in 3rd (overdrive off) it will start doing it about 35 and above. i have heard that lose tranny mounts will cause this but i checked mine and there all tight. i have also read that it can be the torque converted locking and unlocking macking it do this and it can be electronily adjusted somehow? thanks

 

Replace the COP's. I was having same problems with surging at low RPM. Bought set of 8 COP's on Ebay for $114.95 from UNEEKSUPPLY, installed and trcuk runs great. (152K miles 5.4 2005 2x4 Screw)

 

Did you get a battery yet? And did you put ford plugs In?
Also before you change all of your cops I'd test them and save a pile of money.
Get a shop to do a cylinder cut out test to narrow down your problem, then swap two cops (not running mates) and see if your problem follows the cop or stays w the hole.
Have you ever changed your fuel filters?
Ps a pcv valve will not cause this plus you have to buy the whole valve cover to change it. The battery is likely cheaper. If money is tight borrow a friends battery for the evening or get yours tested before replacing it.

 

i used motorcraft platuim plugs (same as stock) and i also just replaced the fuel filter. will most shops be able to test the COP's? it seems to only do it while driving so i dont know if the could check them? i have not got a new battery yet but i did check it and it was about 11 volts (seems pretty low to me). also are you sure you cant change the pcv on the 4.6 with out changing the valve cover? here is a thread of someone doing it.

http://www.f150forum.com/f33/replace...6-v-8-a-23363/

i also had my tranny re-built about 3,000 ago and they put a new torque converter in it. i dont know if the "bump" has anything to do with that locking and unlocking. i read the dealer can fix this but i only read it on one other thread so im not 100% when i make it do the "bump" i can feel it in the seat so im thinking it could be the rear end. i really really want to figure out what is causeing the "bump" because its driving me crazy! thanks for all the help guys

 

I'm not sure about the pcv on the 4.6
I would try and focus on one of the two problems before the other. Don't forget your transmission is electric and funky things can happen with low voltage

 

yea that is true my dad has a 2008 150 and later today when he gets home i will swap batteries to see if it changes anything. im sure i wouldnt hurt to changes it since its 6 years old and has 98,000 miles on it now. im sure it would last through summer but winter might be a different story.

 

ok so i put my stock exhaust back and and that seemed to make the "bump" not quite so harsh. i can still feel it but not quite as bad. my rear end has been whining a little bit lately and i have a bad wheel bearing and my limited slip is not working so im thinking it could be something to do with this hopefully. as far as the surge goes i swaped an amost new battery in out of my sisters explore and it seemed to fix the surge but i havent drove it a whole lot yet so i hope it is gone. aslo the lights dont dim anymore when i rev it and it goes back to idle. now if i steady hold it at about 3000 or so it runs smooth but seems like it has a very slight miss that you can feel because the truck will shake when it misses. could this be the COP's? any help is appricated thanks

 

same thing with mine. cleaned throttle body. fixed it.

 

fixed the bump? or surging and i just cleaned it about a month ago. but i just cleaned the flap and behing it. nothing else