Ok so i have a 99 f150 4.6, latly when im in drive it seems like it will miss or knda studder for a little bit than go right back to normal. and it gets really bad as soon as i turn the A/C on. what could it be? bad fuel pump,relay,filter? any Ideas thanks

 

Mine was doing the same thing the other day so I changed all the spark plugs and wires. It runs fine now.

 

Yeah check your plugs and Coils. I also found a vacuum leak on mine, it was the hose that hooks up to the back of the intake, it had rotted and fallen off. I have a 5.4. Hope this helps!