So my truck has been being a turd lately and im getting like 9.8 mpg with the truck stock. On the highway i have to downshift into 4th sometimes 3rd to get up a hill going 70 even if its not that big. Im wondering if the could be the 02 sensor. I have a check engine light on and off but cant read it following the instructions on the forum. also if it is the 02 sensor do i need to replace the front and rear or just front 02 sensor?

 

Are you throwing a light?

 

light goes on and off was on all ride home today but just went out to a buddies and no light at all

 

I've been experiencing the same thing, CEL keeps going on and off. Been meaning to check the codes....

 

does yours lack power like mine too?

 

How many miles? If you replace the o2's do them all at once.

 

What year is the truck? OBDI only has one oxygen sensor and codes can be read with the instructions at the top of this section. OBDII ('96 and up)has 3 oxygen sensors and have to be scanned for codes.

 

its a 94 and i thought it only had one o2 sensor. when i went to autozone they asked if i wanted the one for before the cat or the one for after the cat which is wierd.

 

Those people only sell parts, they aren't mechanics and rarely will you find one who actually knows what they're talking about. Checking for codes with the instructions at the top of this section should work, you might have done something wrong.

 

well, i guess i'm not really sure. i know my truck isn't running like it should, and hasn't since i got it about a year ago. i haven't concentrated on the engine yet, i really need to. it idles like crap, probably doesn't have the power it should...but the gas mileage isn't too bad, by the sound of it.