Stuttering, Losing Power, 12mpg, Wtf?

[ozziemo27]

Well I'll get straight to the point. My 4.0 OHV is pissing me off, lol. For a while now, I have been getting shit fuel econ, around 11-12.5 mpg and after running for a while say after i get off the highway or after running the trails for a bit, it will start to stutter, lose acceleration, drop below 1000 rpm at idle, gets pretty nutless. I can floor it and it will shift down and stop doing it for a while and i can shut the truck off and restart it and it will stop for a bit. But No matter what, I have been getting 11-12 mpg, and thats pretty outrageous with stock tires which im running for now. What I have done (procrastinator woooo) new motorcraft plugs and wires, plugs gapped to .54 and cleaned my MAF, new fuel filter, and sprayed carb cleaner everywhere and the RPMs didnt jump so i dont think its a vacuum leak. Its throwing two codes. P1131 = Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1 And P1151 = Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2 Where to next?

 

[Spitfire1975]

Did you change your O2 sensors since you are getting O2 sensor codes? Bad O2's will make your truck run rich and run like crap.

 

[Dweano]

Wait you mean 12 mpg isn't normal? Haha...yeah I think I have a problem to then. Then again I also have 33's...and 3.73's. I'd recommend you change the oxygen sensors. I got NTK's and I have no complaints about them.

 

[ozziemo27]

Well that is true but I don't know which one is bad and they're like 30 bucks a piece and theres 3

 

[Spitfire1975]

There is a way to test the voltage on them. Search the tech pages. I just opted to replace mine instead of testing an old O2. you have three....two codes....one for bank one and one for bank two. I would imagine, without seeing your truck, that you have an O2 on each side of the Y-pipe and one somewhere before or after the catalytic converter. Probably have two bad O2's on the y-pipe. Or spend $90 and take care of all of them and don't worry about it. $90 in O2 sensors is better than $400 in cats.

 

[ozziemo27]

Yea there is one on each side and another one... I will see if i can't test the voltage to pinpoint which one but i just won the $500 dollar giftcard giveaway on 4wheelparts.com so I think i will just replace them all. Thanks for your input!

 

[Spitfire1975]

Good Luck!

 

[ozziemo27]

Thanks! I'm pumped!

 

[njdriver02]

im not so familier with the 02 sensors on rangers but I know with other vehicles, the only o2 sensor that effects gas mileage are the ones before the cats, the ones after generally have to do with emissions and check to see if the cat is going its job

 

[ozziemo27]

im not so familier with the 02 sensors on rangers but I know with other vehicles, the only o2 sensor that effects gas mileage are the ones before the cats, the ones after generally have to do with emissions and check to see if the cat is going its job

Well i ordered 3 new bosch o2 sensors for about 120 bucks from partstrain.com. If this doesn't fix the problem, i'll see if its the cats. And if they are causing the problem, clearly i'm going to waste the money on buying new ones instead of cutting them open and gutting them because thats illegal

 

[njdriver02]

if you never changed your 02 sensors, then you will see some benefits, some people say if it aint broke dont fix it, but replacing 02 sensors on a high mileage vehicle makes a lot of sense.

does your truck burn oiil? clogged cat? only wondering because you mentioned you might remove the cat if the 02 sensors dont help

 

[kimcrwbr1]

If your burning oil you need to fix that before you change the cats it will ruin the new ones and I am not sure but clear the computer after you install the new sensors someone here will know if it is necessary and how to do it properly

 

[ozziemo27]

if you never changed your 02 sensors, then you will see some benefits, some people say if it aint broke dont fix it, but replacing 02 sensors on a high mileage vehicle makes a lot of sense.

does your truck burn oiil? clogged cat? only wondering because you mentioned you might remove the cat if the 02 sensors dont help

They could be the stock ones as far as I know. Currently it has 148,000 miles. It doesn't burn any oil *knock on wood*. I don't plan on removing it necessarily.

If your burning oil you need to fix that before you change the cats it will ruin the new ones and I am not sure but clear the computer after you install the new sensors someone here will know if it is necessary and how to do it properly

Doesn't burn oil and I don't plan on buying new cats.

 

[njdriver02]

I am not sure but clear the computer after you install the new sensors someone here will know if it is necessary and how to do it properly

I think if you unplug the battery, it should clear, if not get someone to plug in a obd and wipe it clean

 

[Xandor]

I had the very same problem and replaced my o2's and it helped but didnt go away. Now 10k miles later its getting bad again. I'm cuting my cat out in the next day or two, hope it helps.