02 2.3L bucking studding, and backfiring

[T1m3_Sh1ft3r]

Hello, well i have been dealing with this issue for a little while and have done some things to see if that fixed it. i did a search and somebody mentioned that it could be the alternator which i have a little bit of a hard time believing but it obviously worked for somebody else. But i wanted to see what others think

the issue im having is that the truck is shuddering or buck usually when there is a bit of a load on it (IE 5th gear on a slight incline), when im at about 60% throttle or more, or when its between idle to about 2500 RPM. if im going up hill or at a stop going up hill or heck even at a stop and i have to give it some gas it will back fire some times like crazy. about a month ago I was driving home and it was running so bad that it kicked a check engine light with code P0303(which was caused by crappy spark plugs)

What i have done is ive replaced the plugs (not even about 300 miles ago) and got what came from the factory ones, and ive replaced the coil. i had a very toned down version of this issue a little while ago and somebody suggested that it might be the EGR valve and to unplug the vacum like to see if it was that so i tried it again and only helped a little with the shuddering but not bucking or backfiring. I read that somebody thought it might be the injector that’s just not spraying but dripping fuel into one of the cylinders. Im just not sure what else I should do I dont have a whole lot of money so im trying to avoid throwing a whole lot of money into it is there a way to check the injector or something along those lines im assuming (which I know what that means) that my issues are in cylinder 3

 

[Earl43P]

Most auto parts stores will test your alternator for free, while it is still installed. I'd start there, just to rule it out. While you are there, pick up a fuel filter and replace that.

 

[T1m3_Sh1ft3r]

so i did replace the fuel filter this afternoon, and had the alternator tested( i didnt realize that they could do it while it was in the car ) i also re checked the gaps on the plugs they were in between the .041 to .045. still no luck, but i did an ohms check to see if maybe the wires were bad on the 20k scale this is what i got

plug for cylinder 1 was at 4.8
plug for cylinder 2 was at 4.16
plug for cylinder 3 was at 3.52
plug for cylinder 4 was at 4.97

i know plug 2 & 3 is shorter but not by much maybe an inch or two at most but would that little bit make that bit of difference? especially 3?

 

[54inches]

After doing some searching, I think my 05 is just the iac, but wanted to see if you ever got a resolution.