Prius 2011 with 29MPG trouble!

Sounds like the air/fuel ratio is off, with too much fuel (rich), which obviously uses more gasoline and lowers gas mileage. Some sensors that affect air/fuel ratio include the MAF, MAP, oxygen sensor (located after the catalytic converter), and air/fuel ratio sensor (wideband oxygen sensor, located on exhaust manifold). You could try cleaning the MAF with MAF cleaner since that's easily accessible and something fairly common to do.

I don't have the Torque app. But on my car, using a Bluetooth OBD reader and OBD Auto Doctor app, I'd get a freeze frame that included lambda, which is a way of describing air/fuel ratio (less than 1 is rich, more than 1 lean). For example:

Bank 1 - Sensor 1 (wide range O2S): Equivalence Ratio (lambda): 0.994

On my car, just before I bought it at 150,000 miles, the previous owner had reported low gas mileage to the dealer. Eventually it popped a check engine light and was fixed after replacing the MAF (maybe a cleaning would have worked too?) and air/fuel ratio sensor. I bought the car just afterwards, the gas mileage was fine.

I wouldn't throw parts at it. Seems like you'd replace a lot of possibly good parts (your 12V battery?). Take it to a shop for diagnosis. Seems like something that any shop that could do emissions testing could do (though maybe not a thing in Jordan?). Back when emissions testing was required in my state, my old Subaru once needed an oxygen sensor or something like that to pass the test. Or drive it until you get a check engine light and code telling you what's wrong.

 

That stinks, no schrader valve like on some GM cars. The manual says to disconnect the line and install a tee for the pressure gauge.

44 to 50 PSI is the standard fuel pressure

Pixel XL ?

 

Yeah I just took a look through the Repair Manual, came to the same conclusion. It says to disconnect fuel line at the pump, patch in hose with Tee and pressure gauge, as you said. There's also mention of Techstream.

 

Good to know my memory is not as bad as my wife says it is from time to time .

 

Does she say the same thing about your hearing?

 

Selective .

 

Check your brakes, make sure all yours pins are greased up properly. A dragging pad can kill mpg. Check emergency brake operation. Make sure your egr pipe/cooler and intake manifold are clean. Change your spark plugs or at least check them. If someone put cheap plugs in, they could be burnt up by now. A car burning oil will also foul your plugs in a result of bad mpg. Send out your injectors to be cleaned/tested.

 

Not as good but worth a try: try an injector cleaner, one you add to the tank at fillup, with PEA (Poly Ether Amine IIRC).

 

Did you try that MAF cleaning?

 

How are the tires wearing? Alignment

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That smell of gas could be a good clue, maybe. It's running rich for some reason. Has anyone mentioned the Oxygen Sensors: there's two of them in the exhaust, one before and one after the catalytic converter. They would likely show a warning light and code if they were out of parameters, but maybe they're just on the edge, not quite failed. I am just guessing though.

 

I had a smelling gas problem in another car, it turned out to be a bad fuel pressure regulator.

 

Maybe other can glean something, I'm pretty clueless.

 

What I forgot to add here might very well be the problem. The EVAP system vacuum switching valve (also called purge valve) was also sticking open sometimes, letting in unmetered air leading to a lean condition. So check that valve. It's the same thing discussed in this thread:

Engine behaving strangely and popping hoses off intake manifold | Page 2 | PriusChat

 

@anonymous described testing with a 12V battery in that thread (post #30) to see that it was sticking. I don't have my Prius anymore, so I can’t double check, but I remember the valve being easy to access/in my face when cleaning the EGR circuit. Maybe you just need the airbox off to access it? I never played with it myself - just recalled seeing the fault described in the Toyota service records from before my ownership.