MilesWeb Hosting Forum

First of all, you need to login to the google webmasters to identify the errors.
There are majorly two sections
1. Site Errors and
2. URL Errors.
You have to figure it out first what type of error you are getting. And for that, you need to go to the Crawl Errors section. In the Crawl Errors section, you get the complete list of errors from which you can easily identify what type of errors you are getting. That means whether they are Site errors or URL errors.

If you try to remove manually, then also Google takes a time to remove the 404 errors from its index. Therefore, I will advise you to leave as it is.

Does 404 error page effect the ranking?

Yes, it does affect the website organic ranking because it delivers a bad user-experience to visitors.

As mentioned above, there are two types of error, but in that also there are sub types of error:

Site:

i) DNS Error
2) Server Error
3) Robots Failure

URL:

1) Soft 404
2) 404
3) Access denied
4) Not followed
5) Server error and DNS error

Find which error you are facing and get a proper solution to it.