The book may call it an air flow meter, but it is the same thing as a MAF sensor. It is bolted to the top of the air cleaner housing.
Ten mile drive is barely getting the engine warmed up, it could be running in open loop for much of that time which will negatively affect gas mileage. Then it transfers to a high load/high speed mode that also dumps extra fuel into the engine. But even then seven mpg sounds really low. Was this something that just happened or has it been getting poor mileage for the entire time you owned it?
You mention it is running rough. That could easily be the result of extra fuel being injected, to see that though you need a scan tool that can read live data, specifically the fuel trims and the AF ratio sensor signal. Those would tell you what the computer is seeing with regard to fuel flow and engine load.
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Tuesday, May 8th, 2018 AT 10:18 AM