Bad gas mileage

Hello all, I just purchased a 2002 Taco, 2.4 5 speed and I'm getting 11 miles per gallon. I installed new plugs, cleaned MAP sensor, and throttle body, checked for vacuum leaks, checked for any fuel leaks. Also check engine light reads a 171 code (lean fuel). Not sure what to check next. I'm thinking a problem with injectors or fuel pump.

 

Its p0717 lean bank 1?
If ao I believe that has to do with you o2 sensor. Maybe this can help you https://parts.olathetoyota.com/p0171-code-toyota

 

What tires are you running?

 

He is a 5lug so i doubt its big tires

 

A 2.4L 5 lug running 33" mud terrains (if you could get them to fit, lol) should manage 20mpg without effort.

As the above link suggests, since you've already cleans the MAF, check for vacuum leaks and then replace the upstream O2 sensor if you don't find vacuum leaks.

 

Terry, do you have access to a obd2 scanner? If so, you need to look at the live data section and see what your fuel trims are doing based off of your p0171 code. I cleaned a mass air sensor before and had same issue so, I replaced it with a new one and it fixed the issue

 

This might help.
https://www.youtube.com/watch?v=bKGI9N_yWd0

 

How about any of the available fuel injector cleaners available at any auto parts store? I like to use Marvel Mystery Oil for fuel injector cleaner on my truck.

 

Agreed, first thing to do is get rid of the check engine light, that alone (no matter what the code) will affect gas mileage as it's in limp mode. And with a faulty o2 sensor that plays a big role for gas mileage.

 

Thanks for all the replies. going to try cleaning the injector, checking both O2 sensors, and I ordered a scan reader. everything is stock. No big tires or lifts. I think the upstream O2 sensor is bad. At least that's what the previous owner said when I asked him about the terrible gas mileage.

 

The upstream sensor controls the mix, downstream just tests the cat.

 

just because you're not running big tires, doesn't mean you should dismiss them as a problem. Under inflated tires and a bad alignment - even if it feels aligned - can kill mpg's.

 

not to the extent that the OP is experiencing. OP says he's getting 11mpg in a 4cyl 5 lug. That's 1/3 what he could be getting. PSI and alignment could be a contributing factor, but a relatively small one.

 

I second that, my 02 prerunner 3.4 auto with 285s avg is 18.5mpg. I run 30psi front & 25psi in back.

 

UPDATE: Thanks for all the input. I pulled the Upstream O2 sensor and it was full of carbon. Pulled plugs and they were also full of carbon. After removing and testing the Mass Air Flow sensor I found it was bad. Replaced it, O2 sensor and installed new plugs. My Taco now runs the best its ever ran, and no codes. I also used some seafoam in the intake to help clean up some of the carbon. I haven't yet tested it for gas mileage but I will keep you all posted. Thanks

 

If your 02 sensor was plugged, there is a good chance the catalytic converter could be too. Seems like you got it figured out, but if it persists thats where I would look next.

 

^^concur. PO left alone for so long that cat is probably on its way out.

 

Well its running great BUT, check engine light came back on after driving about 30 miles. Haven't done a scan yet to the read code. The search continues $300+ already spent. I'll keep you all posted.

 

Blue if the Cat is bad wouldn't it give off a code? How do I check if the Cat is clogged or bad. I think it has two. My multi meter has a temp reader laser beam. would that work if I checked the temp before and after the cat and they were not that far off from each other?

 

Thats a little beyond my knowledge. I only know that is a cause of bad mileage, combined with how much carbon was on your 02 sensor. It would nost likely throw the same 02 sensor code, as the downstream sensor wouldnt be picking much up.