I have 2005 , 5.7, Durango. 300k+ miles on it.. When accelerating the check engine light flashes and and the truck shutters and shakes until you get to a higher speed. This was happening between 50-60 mph.

We did have new plugs put in and it helped for about a day. And now it does this between 30-40 mph.

What could be causing this?

It did through a code about an o2 sensor.

Any feedback would be appreciated

 

CEL flashing is telling you that you have one (or more...) cylinders misfiring. If you are also getting an O2 sensor code, try disconnecting the front O2 sensor(s?), see if the problem goes away. If it does, replace the sensors. (NTK or Denso sensors only please, skip bosch, Dodges don't like 'em.)