Under what circumstances does it "pop up"? And what exactly do you see when it does?
Taskeng.exe is a legitimate Windows program. It is, as you saw, the "Task Scheduler Engine."
Of course, malware can have any name and malware authors often use the name of legitimate files in order to fool people who look using tools like the Task Manager.
If MalwareBytes AntiMalware says your system is clean, you're probably OK. If you want another opinion, run the free ESET online virus scanner: https://www.eset.com/us/home/online-scanner/
You can also search for taskeng.exe. You should find at least one instance of taskeng.exe in C:\Windows\System32
If you have a 64-bit system, this file should be about 453 KB in size and if your system is up to date, it should be version 6.1.7601.17514 (right-click on the file, select "Properties" and look at the "Details" tab).
If you have a 32-bit version, the size will be about 187 KB with the same version.
A 64-bit system will have two copies of the 64-bit version of taskeng.exe and two copies of the 32-bit version:
If you find a file named taskeng.exe that is in a different location or is a different size, upload it to VirusTotal for a free check: https://virustotal.com/