4.9 sputtering and idk why
 

I got a 91 4.9 and it has a weird skip/sputtering, its not on a regular cycle like one cylinder, it just does it when it feels like it. What is this? I ran seafoam through it and got a k&n drop in lately too...Just saying. Any help is appreciated. Thanks.

How long has it been since you your air filter, spark plugs, plugwires, were replaced? If it is truely random you might also want to check your ground connection.

After that i think anybody here would tell you the next step in isolating the problem would be to check for error codes. The steps for doing that are here https://www.f150forum.com/f10/how-re...es-obdi-10907/

Good luck.

Is it jerking/shuddering when under accleration? Could be a pinhole in a vacuum line as well. But I'd check Pine's suggestion first.

it could be a number of things. first thing to check is the spark plugs and replace plugs, wires and distributer cap all at once if they seem worn out. if it still persists next i would check is 02 sensor. if its over 80grand on the odometer since the last one its a good idea to replace it. it would throw an engine if it was bad though... other than that check vaccuum lines(especially if ur cruise control doesnt work it would point to this since cruise works off vaccuum lines) after that i would say check for faulty gaskets in the throttle body/upper plenum/ intake manifold, or else maybe even could be a bad cat or two. after that the only thing i could think of is a fuel pump going bad or just plain old bad delivery. if theres a code it would be hella easier though to pinpoint whats wrong.

ok Well i will go ahead and say that plugs and dist cap are fairly new but idk about wires, just got a new air filter, and i think vacuum lines are good, cruise control works. I will check codes soon, i have checked it before and posted the codes i got but nobody really helped. I will see if i can check for codes again.

i have a 1992 i had a idol problem solved it myself with throttle body cleaning front and backside cleaned with carb cleaner and small wire brush removed 18 years of junk was a mess no more eratic odol etc. runs super now .. good luck

I would do these steps exactly in order!!! Definately spark or sensor (probably o2) try to check for codes before u start checking around for leaky gaskets and fuel pump