Delete lines VBA macro takes a significant amount of time - excel

Question

I have a macro that deletes lines based on a certain value in a column and then sorts them. It works fine. However, the worksheet starts with about 4000 rows and the macro ends up deleting about 2000 of them and it takes 1 minute 25 seconds to do it. I'm wondering if there's something I can do that will make it take a lot less time. Here's the code:
'remove numbers that are not allowed based on values in "LimitedElements" worksheet
For i = imax To 1 Step -1
a = Sheets("FatigueResults").Cells(i, 1).Value
Set b = Sheets("LimitedElements").Range("A:A")
Set c = b.Find(What:=a, LookIn:=xlValues)
If Not c Is Nothing Then
Sheets("FatigueResults").Rows(i).EntireRow.Delete
End If
Next i
'delete unecessary or redundant rows and columns
Rows(3).EntireRow.Delete
Rows(1).EntireRow.Delete
Columns(23).EntireColumn.Delete
Columns(22).EntireColumn.Delete
Columns(21).EntireColumn.Delete
Columns(20).EntireColumn.Delete
Columns(14).EntireColumn.Delete
Columns(13).EntireColumn.Delete
Columns(12).EntireColumn.Delete
Columns(11).EntireColumn.Delete
Columns(4).EntireColumn.Delete
Columns(3).EntireColumn.Delete
Columns(2).EntireColumn.Delete
'sort data
Dim strDataRange As Range
Dim keyRange As Range
Set strDataRange = Range("A:Q")
Set keyRange1 = Range("B1")
Set keyRange2 = Range("G1")
strDataRange.sort Key1:=keyRange1, Order1:=xlDescending, Key2:=keyRange2, Order2:=xlDescending, Header:=xlYes
'delete rows that are not in the included values For i = imax To 2 Step -1
If (Cells(i, 2).Value <> 0.04 And Cells(i, 2).Value <> 0.045 And Cells(i, 2).Value <> 0.05 And Cells(i, 2).Value <> 0.056 And Cells(i, 2).Value <> 0.063 And Cells(i, 2).Value <> 0.071 And Cells(i, 2).Value <> 0.08 And Cells(i, 2).Value <> 0.09 Or Cells(i, 3).Value <= 0) Then
ActiveSheet.Rows(i).EntireRow.Delete
End If
Next i

Answer 1

Add this at the beginning:
Application.ScreenUpdating = False
Application.EnableEvents = False
Application.Calculation = xlCalculationManual
Add this at the end:
Application.ScreenUpdating = True
Application.EnableEvents = True
Application.Calculation = xlCalculationAutomatic
Also, instead of
If (Cells(i, 2).Value <> 0.04 And Cells(i, 2).Value <> 0.045 And Cells(i, 2).Value <> 0.05 And Cells(i, 2).Value <> 0.056 And Cells(i, 2).Value <> 0.063 And Cells(i, 2).Value <> 0.071 And Cells(i, 2).Value <> 0.08 And Cells(i, 2).Value <> 0.09 Or Cells(i, 3).Value <= 0) Then
ActiveSheet.Rows(i).EntireRow.Delete
End If
Use
Select Case Cells(i, 2)
Case 0.4, 0.045, 0.05, 0.056, 0.063, 0.071, 0.08, 0.09, Is < 0
'Do nothing
Case Else
ActiveSheet.Rows(i).EntireRow.Delete
End Select

Answer 2

I much prefer to build a string of rows to be deleted then do ONE delete. Here is a sample I put together for another post on here yesterday:
Sub DeleteRows()
Dim i As Long, DelRange As String
For i = 1 To Cells(Rows.Count, 6).End(xlUp).Row 'Doesn't matter which way you go when you delete in one go
If Left(Cells(i, 6), 3) = "314" Then DelRange = DelRange & "," & i & ":" & i 'Change the "314" as you see fit
Next i
Range(Right(DelRange, Len(DelRange) - 1)).Delete
End Sub
Also no need to worry about turning calculation or screen updating etc off when you only perform one deletion