VBA to read in tab delimited file - ado

Question

I have some code which reads in a tab delimited file where cell reference B2 matches the reference in the first column in the tab delimited file. This works fine where the text file is small. The below works on a sample file with aa bb and cc as the headers with dummy data.
Option Explicit
Sub TestImport()
Call ImportTextFile(Sheet1.Range("B1"), vbTab, Sheet2.Range("A4"))
End Sub
Public Sub ImportTextFile(strFileName As String, strSeparator As String, rngTgt As Range)
Dim lngTgtRow As Long
Dim lngTgtCol As Long
Dim varTemp As Variant
Dim strWholeLine As String
Dim intPos As Integer
Dim intNextPos As Integer
Dim intTgtColIndex As Integer
Dim wks As Worksheet
Set wks = rngTgt.Parent
intTgtColIndex = rngTgt.Column
lngTgtRow = rngTgt.Row
Open strFileName For Input Access Read As #1
While Not EOF(1)
Line Input #1, strWholeLine
varTemp = Split(strWholeLine, strSeparator)
If CStr(varTemp(0)) = CStr(Range("B2")) Then
wks.Cells(lngTgtRow, intTgtColIndex).Resize(, UBound(varTemp) + 1).Value = varTemp
lngTgtRow = lngTgtRow + 1
End If
Wend
Close #1
Set wks = Nothing
End Sub
I am trying to get the below bit of code to work using ADO as this will run much faster on a text file with a couple of million records however I am getting an error on the '.Open str' part of the code (no value given for one or more required parameters).
It looks like it is to do with how I am defining the string- could you review and see if there is something I am missing...?
Sub QueryTextFile()
t = Timer
Dim cnn As Object
Dim str As String
Set cnn = CreateObject("ADODB.Connection")
cnn.Provider = "Microsoft.Jet.OLEDB.4.0"
cnn.ConnectionString = "Data Source=C:\Users\Davids Laptop\Documents\Other Ad Hoc\Test Files\;Extended Properties=""text;HDR=Yes;FMT=Delimited;"""
cnn.Open
Dim rs As Object
Set rs = CreateObject("ADODB.Recordset")
str = "SELECT * FROM [test1.txt] WHERE [aa]=" & Chr(34) & Range("B2") & Chr(34)
With rs
.ActiveConnection = cnn
.Open str
Sheet1.Range("A4").CopyFromRecordset rs
.Close
End With
cnn.Close
MsgBox Timer - t
End Sub