4.2 f150 01' i have a problem truck shakes & seems like backfires out of manifold like small explosion on driver side. When it RAINS it gets worst doesnt accelerate backfires really bad very slow on picking up speed & when i try to floor it, the check engine MIL starts blinking did scan once had misfire codes & both lean banks codes but recently havent check them. HAS ANYBODY ENCOUNTERED THIS SITUATION ????? Really like to just get that problem solved STUMBLES / SHAKES / MISFIRES / BACKFIRES / accceleration really slow, any ideas; thanks in advances!!!

 

How many miles and did you do anything about the misfire codes when you read them?

 

Well i did nothing about misfires. I dont know if its cuz there is a vacuum problem & moisture goin into eng. or whats happening i did do a vacuum test in park at idle or as per vacuum kit said around 2k rpm but kept a steady pressure. really at idle everything fine but when in gear it sort of stumbles now all the time, slow accelaration but now hurricane season in mode i need to get this problem solved ASAP cuz it really gets bad misfires, bogs really bad dont understand why it gets worst when rain if as some rain gettin in eng. or plugs, wires, vacuum dont know!. any ideas where to start or what is of this problem... Thanks for any responses. sorry if to long.

 

I would start by changing plugs (MC) and wires remove the coil pack and check for cracks on the bottom. Then check for vacuum leaks.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>