I've a 2007 Honda civic (automatic transmission). I had to replace the starter in the car couple of days ago. After the replacement, I feel like I have to press the gas more than before to expect acceleration. At some degree, I don't even get the expected acceleration. The acceleration rate has been changed significantly. What can possibly cause this problem?
A routine replacement of the starter motor would not cause an increase in fuel consumption or effect its acceleration. You may have an incorrect replacement motor, or defective motor staying engaged and causing the symptoms you described. Otherwise, starter bolts fitted in the wrong position and jamming on the engines ringgear. Connections such as vacuum hoses removed for accesss reconnected in the wrong position. You need to go over the replacement from start to finish to determine what is wrong.