Not enough FUEL? Help (UPDATE)

Hey guys, new member here. I have a 2010 tacoma 4wd v6. Bought it off the lot. I have come to this forum many times for mods and info, but I had to create an account this Time.

My toyota has never given any trouble whatsoever, cant complain with 250k miles. However she is now in the garage and throwing an engine light code po171 & po174 “too much lean”.

some info—- about a month or two earlier i was driving along just fine, no prior problems with HP or engine, when my truck Suddenly stopped accelerating and came to a stop (would idle just fine). Restart engine and it would go a little further and same thing again. Made it home and swapped some relays and reset the battery and didn’t have any issues since ( just luck i assume) . 1 month later: same thing.. except this time it wont go any more. It will crank fine and idle for up to 20 seconds or so and then sputter out like it is out of gas.

my first thought was the fuel pump- i called the dealership and the guy said he could count on one hand the number of fuel pumps he has replaced, and he’d been there 10 years. But of course nothing mechanical is concrete.

any suggestions guys/gals? Im to the point where I am going to start having to guess what is wrong with it - repair it - and hope for the best. Any questions about the vehicle i would be glad to answer them in return for information. Thanks guys im stumped!

 

Check all your vacuum hoses.
Check the PCV valve.
Check for Exhaust leaks.
Check the MAF Sensor
Check the fuel System- Pressure
Check the A/F Sensors. (Not likely the issue)

 

Thank you I will check all that you listed

 

Check the fuel pump resistor.

 

If it's the fpr, you can bypass it with a jumper/wire, "apparently ".

 

might as well add to the list
o2 sensor
injectors
crank sensor

 

Is the fuel pump resistor in the fuel tank or under the hood. Thanks for the info everyone

 

Under the hood

 

Thanks for the diagram sir

 

FWIW, I’m going to doubt it is the resistor.
If it were me, I’d be checking the MAF and the fuel pressure.
With your mileage, It’s really not that uncommon for the fuel pump to be weak, or have a partially clogged filter.

 

Thanks. Ive read that ‘too much Lean’ could be too much air or too little fuel.. but my gut is telling me its fuel related

 

Yes, that is typically what causes the lean condition.

The MAF monitors the amount of air entering the engine.
The A/F sensor monitors the air coming out of the engine.
If air is entering the intake AFTER the MAF Sensor, then you’ll have too much air and not enough fuel.
The MAF Sensor didn’t know to calculate for the “extra” air, and the injectors don’t allow enough fuel for the “extra” air.

Next, could be restrictions in the fuel system. Lean.

Another thing to look for is an exhaust leak BEFORE the A/F Sensor.
This will “see” too much air out of the engine. This too is Lean. But not caused by a fuel issue.

There is a lot more to the actual workings of MAF and A/F Sensors.
But that is the basics of the system.

Even I have a hard time comprehending the the actual working of the new EFI Systems. Alien Technology to me. Lol

 

Thanks again, Sounds like it could just as easily be the MAF sensor

 

It should be easy enough to try.
Here is a good DIY, I’d read the whole post.
https://www.tacomaworld.com/threads/2009-2nd-gen-maf-cleaning.530945/

 

Start by cleaning the MAF.

Fuel pumps on 2nd gen tacomas aren't SUPER rare, but are unlikely.

That said, it sounds like it. These trucks like to fail odd, they will idle and get to 30mph, but then fall on its face.

There's usually no codes, but if it is lean, its mega lean, like +99%

Fuel pressure gauges are hard to hook up without the special fittings, but you can hook a universal up to it without it running to see if it can make 44psi.

 

Thanks guys. Going to clean the MAF this evening. It has never been cleaned so that would be nice if thats all it is. Bishop- Did you mean it sounds like Fuel pump or the MAF?

 

I you clean the MAF, make sure you are using only MAF cleaner.

 

MAF didn’t really look dirty. I will say that one side of the needle was flat black, but not necessarily burnt.. possible buildup? I assumed it came from the factory that way, the other side looked like a normal thermometer. VAC Hoses looked good.

if i resort to the fuel pump.. is it easier to drop the fuel tank or pull off bed ? I know some vehicles are different

 

I'd have it tested, its not easy to change. The bed doesn't come off easy at all. You drop the tank and swap out the pump on Tacoma.

 

So if i turn the key over, but not running.. the fuel pressure should read 44 psi?