I have a 2013 GMC Sierra 1500 WT with a 4.3 liter engine and 97k miles. My gas mileage started dropping all of a sudden recently, so I replaced the air filter and the MAF sensor, hoping it would solve the problem. It didn't. Since it was overdue for a tune-up, I took the truck to a mechanic who replaced the plugs and wires, cleaned the fuel system, and checked the oxygen sensors. He said the sensors showed to be working, so he didn't replace them. All this still didn't solve the issue. By process of expensive elimination, does this point to my fuel injectors as the problem? I'm at a loss on what to do next. It's using nearly twice as much gas as normal.
Don't replace any more parts and take it to a better mechanic. Have it scanned by someone who knows what the heck they're doing. Replacing parts without proper diagnosis is futile. The FAQs might shed some insight for you.
does this point to my fuel injectors as the problem?
Not neccessarily.
But a well equipped mechanic should be able to run a fuel injector balance test with a good diagnostic tool to find out.
They could also measure exhaust backpressure to test for a failed catalytic converter and more furl trim diagnostics to see what your mixture is doing.
I think you need competent mechanic who will actually fix your problem.
