OK so i go to start my truck and it is idling horribly. i start checking spark plugs, injectors etc. replaced spark plugs and still wont help anything, the only cylinders firing are 1 and 4. 2 and 3 had oil on them when i pulled out the old plugs. then my check engine light came on around the time that i started it up and found the idling problem, i ran the code and it said bad o2 sensor, i figured no prob, replace it and everything will be fine. i replaced it but nothing changed, it still ran the same code and the idle is still sh**.
also a random thing happened as well, my speedo indicator is all the way on the right hand side and now will not show what my speed is. i need help!!!....... and this is my first post so hi guys!