ok the past week my trucks been bucking a low rpm when driving.
if i get behind someone slow second and 3rd around 1200 1500 rpm it bucks feels like its missin but it idles fine and cruises fine n if im not behind some one slow n i take off normal its fine.

its a 90 f150 4.9 t18 ive dun the fallowing to it within the past 6 months
new plugs and gapped right
timed right
cap rotor wires coil
got a tps egr position sensor and iac valve from a running engine
new fuel filter blew out the fuel lines chem dipped and rebuilt injectors with new orings nossel and filters
new vacuum lines and fuel pressure regulator
rebuilt altinator
new timing set
oil filter
pcv valve
new air filter
ne flywheel clutch pressure plate throwout bearing slave cylender clutch hose
new radiator new pads rotors bearrings rear shoes and drums
rebuilt the rear new universal joints new thrmostat
cleaned the trottle body new cat back exhaust

now this didnt start after i did all this it started 2 months after i did all this
i inspected all my plugs a replaced them again to be sure same with cap rotor and wires

im stumped and i work on the shore so its alot of stop and go and them damn sight see'ers that drive 5mph so goin to and from work pisses me off when it starts bucking

now my battery light is on im pretty sure its the battery im going to get a new one when i get the cash could that be screwing with the ignition or could it be the ignition modual?

 

Lemme know if you get this one figure out, I have had this same sort of problem for like ever, but never had the time or money to figure it out.

 

will do im friggen stumped i dont know what it could be

 

I have a slightly used IAC I'm gunna swap on tomorrow and see if that does anything, don't know why it would, but it was free so why not.
I also want to see if the mine is all clogged up again since it's been a month since I cleaned it.

 

You know mine does the same thing now, been doing it for mabey a week all of a sudden. I give it a little more gass and it seems to stop, but then I get yelled at by my fiance and have to let off
I thought it was the trq of the 4.9L that was doing it...but I would like to know why mine does it as well now.

 

Alright 50 bucks to whoever figures it out first.
Mine has done it since day one but seems like it does it more often since either exhaust, tune up, or new computer. All of those were done within a short period of time so I have no idea which would cause it to get worse.
Or better, it actually seems like its less of a buck, but more often. Before it seemed like all power cut out and now it's minor and cuts in and out until I either push the clutch in or hammer down.

 

pretty much i checed my iac still free so i dont know what it is

 

That sounds more like an alternator problem. I'd suggest you run over to the parts store and get the alternator and battery tested.

 

just put an altinator on didnt test the battery but it starts the truck up just fine everyday

 

Looks like I'm not gettin any work done on the truck today, gotta go to work.
So someone else figure this problem out already.

 

timed right? 6 months ago, or timed now? ...
sounds like something with fuel..

 

timed with a timing light about a month and a half ago 10 degeese before everything in the fuel system is either new or rebuilt except fuel pump but if it were that id assume it would do it worst speeding up but speeding up its perfect its just a slight miss/buck at low rpm if im behind someone who dont know ware the go pedal is if i drive normal its fine and it idles perfect at 700 rpm factory spec

 

yeah, id probably go with charging system, I don't see how it would be the battery, it self, seeing as the alt would pick up for that, I wonder if it isn't over charging... They really should make cars/trucks ect like they used 2...

 

had 2 diffrent altinators the light came on so i had a good one i rebuilt for a spair so i swapped that in n the light stayed on but sometimes if im idlein for a wile like if im at the bank the light will flicker and or go out for a wile then when i start driving it come back on

 

Voltage regulator maybe? Or the belt is slipping.