Eliphaz has advised Job that he should confess his sins and beg mercy from God. If Job cries out now and goes through the empty motions of repentance for wrongs he's convinced have not occurred he's simply reaching out to God again for reward in the form of relief from his trials.
This situation doesn't make every plea to God for mercy or relief an expression of evil, but in this morality story, Job is certain that he has not brought this on himself. To go to God with an empty confession signifies a relationship where one's connection to deity is purely based in what one gets in return. This was Satan's argument to God. So what will Job do, will he take the advice of Eliphaz or maintain his innocence?
We see his reply in chapters 6 and 7. Job's misery invokes great feelings of pain. The man is at his end. He cries out to God in his reply, but not as a bargain begging for an end to suffering in exchange for a plea of guilt. Job seems to cry out that suffering is the plight of humanity. He pleas with God to see his suffering and ease up on him a bit. He doesn't claim that humanity is free from sin and deserving of favor from God, but he questions why humanity would be deserving of such hardship. He seems to be moving toward a reasoned argument with God that perhaps things have gotten out of hand; he understands that this world will bring troubles, but why must we suffer just for being alive.
Eliphaz' words offered no consolation for Job. Lucky for him he's got two more friends among him.