I deployed a custom made solution to the SharePoint 2010 Central Administration application. However when I tried to remove the solution and failed from both PowerShell and GUI. The solution remained in the Deployed state. After examining the log files I figured out that SharePoint timer iterates all the web applications except central admin.

Here is the PowerShell script to remove a solution that was deployed to Central Admin Application.

# check to ensure Microsoft.SharePoint.PowerShell is loaded
<pre>$snapin = Get-PSSnapin | Where-Object {$_.Name -eq 'Microsoft.SharePoint.Powershell'}
if ($snapin -eq $null) {
  Write-Host "Loading SharePoint Powershell Snapin"
  Add-PSSnapin "Microsoft.SharePoint.Powershell"
}

$centralAdmin = Get-SPWebApplication -includecentraladministration | where {$_.DisplayName -eq "SharePoint Central Administration v4"} | select Url
$solutionName = Read-Host "Please enter your solution name (e.g. MySolution.wsp)"

Uninstall-SPSolution -Identity $solutionName -WebApplication $centralAdmin.Url -Confirm:$false

Hope this helps!