No idea what's wrong

[csnider14]

I'm having an issue when I'm holding speed, the truck starts shuddering and starts losing power then picks it back up and starts all over again. On the interstate it will shift back and forth It's like it loses torque at cruising speed. I recently did a tune up on it and it ran perfect for a while them started this. Is this a transmission or engine issue? Please help! Thanks

 

[Turdle]

How did it run before the "tune up". Did it have the same symptoms?

When you say tune up I assume new plugs and wires-fuel filter, air filter -

 

[csnider14]

It shuddered the same way but it did it all the time. I did plugs and wires only

 

[corkey]

check engine light on yet ?

 

[csnider14]

Yeah but it was on way before this for both banks being lean, I just changed all the O2 sensors and the light came right back on and I haven't gotten the chance to read the code yet

 

[inkjunkie]

check engine light on yet ?

x2

 

[koda2000]

running lean sounds like you have a vacuum leak. intake manifold gaskets are a likely suspect, but first check all other possible sources (lines, hoses, PCV grommet & elbow).

how many miles on your fuel filter? if more than 20K i'd change it.