password entry keystroke delay

im hoping someone on these forums can help me here. my macbook air is about 2 months old, and only had light use. yesterday i had a pop up to install MacKeeper and since then the log in screen is not working properly 😟. when you try and enter the password there is no response unless you hold down the key for about 3 seconds. I have removed MacKeeper using a malware remover but the log in issue persists. Does anyone now what this issue is and how to fix?? Many Thanks