Need Info! CEL and poor mileage

[piggy]

Just joined here and have a few questions.
I just recently purchased a 2000 4runner 4x4 with 115k miles, auto tranny. The PO did the timing belt, water pump and a few other items at 100k. The CEL was on when I got it so I changed the following, all belts, plugs, wires, valve cover gaskets, and brakes (pads and rotors). I then got a P0171 code so I changed the 02 sensor along with the TPS. The CEL then went away. I go to get it inspected and the CEL came on again! I then replaced the MAF.
CEL light went off for about a week. Now its back on and I only got about 170 miles before my fuel light came on.
Just wondering if you all had any ideas on how to trouble shoot my problem.
Also a fresh oil and filter change last week as well.
Sorry for the long winded post.

 

[piggy]

forgot to add, I am running 32 BFG AT's. No lift right now, it goes on friday. OME 3 inch! Pics to follow.

 

[BrianSD_42]

The CEL was on when I got it so I changed the following, all belts, plugs, wires, valve cover gaskets, and brakes (pads and rotors). I then got a P0171 code so I changed the 02 sensor along with the TPS. The CEL then went away

Dude for all the money that you are spending... ... get a ScanGuage for $160 on Amazon and post the code / lookup the code. There is no point going back to the mechanic until you do this.

 

[piggy]

sorry, I did that. P0170. System too lean, i think. I also wanted to replace all that stuff to start fresh. I got a hook up at an auto parts place so Im not spending too much money on parts. I searched all the threads on the code here and on other websites and from what I gathered it is either the O2 sensor or the MAF, both of which are replaced.

 

[Martinjmpr]

3rd gens are notorious for having bad fuel gauges, so if your low fuel light is the only indication that you're running out of gas, it doesn't mean you are.

How much fuel do you put in? Do you normally fill your tank up to the top every time? Do you calculate your mileage by taking miles driven and dividing that by gallons used?

Last time my low fuel light came on I put a hair under 15 gallons in to fill it to the top. That means I had nearly 1/4 tank when the fuel light came on. Even at 15mpg I could have gone another 50 miles.

I think the CEL and fuel issues are separate. You need to determine your actual MPG first and then work towards resolving the CEL problems.

BTW, don't forget to check your odometer to see if it's accurately measuring distance, chances are good that it's not. Best way to do this is with a GPS (on the assumption that the GPS is more accurate.)

Set the trip meter on the GPS to zero, then set the trip meter on the truck to zero. Drive about 100 miles and then look at both trip meters. Since you have slightly oversized tires, most likely the miles shown on the truck will be lower than the ones on the GPS.

Take the difference between the two numbers and divide it by the number on the truck's odometer. That is your conversion factor.

Example: Truck odometer shows 100 miles, GPS shows 103.5 miles. Difference is 3.5. Divide 3.5 by 100 and you get .035. Your conversion factor, then, is 1.035. IOW, every time your odometer shows you going 1 mile, you actually have gone 1.035 miles.

Fill the tank full, set the tripmeter to zero. Drive around as normal. After the low fuel light comes on (if you want to wait that long), fill up again, all the way. Take the total miles driven and multiply by the conversion factor. That will show you the actual miles driven, and then divide that by the number of gallons you put in for your real MPG.

BTW, it helps if you always fill up at the same gas station and in the same manner, i.e., if you fill until the pump stops automatically the first time, or the second time, then always do it that way.

 

[MAD 69]

Your getting 150 miles and your fuel light goes and your still planning on getting a lift? I would fix everything that is wrong with it before worrying about a lift, what if you can't fix the truck and you have to get rid of it?

 

[piggy]

martinjumper- I always fill up the same way at the same gas station. I have yet to use my gps, but I will do this on the next thank. Thanks for the advice on that.

Mad69- I already have the lift so its going on regardless of the mileage. And unless there is something horribly wrong with the runner, I have NO plans of getting rid of it.

Is there anything other than the MAF and/or the O2 sensors that would cause the P0171 code?

Thanks again guys-

 

[kakarot]

Piggy, here are some other things that you need to look at, I also has the same code as you but right now I'm kind of short on cash to afford an 02 sensor bank 1. I will let you once I fix it by the end of June. If you do get it fixed before me let me know. Good luck

P0171
When air fuel ratio feedback is stable after engine warming up,
fuel trim is considerably in error on RICH side
(2 trip detection logic)
Air induction system
Injector blockage
Mass air flow meter
Engine coolant temp. sensor
Fuel pressure
Gas leakage on exhaust system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
PCV valve and hose
ECM

martinjumper- I always fill up the same way at the same gas station. I have yet to use my gps, but I will do this on the next thank. Thanks for the advice on that.

Mad69- I already have the lift so its going on regardless of the mileage. And unless there is something horribly wrong with the runner, I have NO plans of getting rid of it.

Is there anything other than the MAF and/or the O2 sensors that would cause the P0171 code?

Thanks again guys-