sudden mpg problem

[suthrnchvyguy89]

about a week or two ago my truck started gettin horrible gas mileage and im not sure why. its always been bad but recently it is easily twice as bad as it was before.

i already changed the spark plugs and wires to see if that would help... it didnt lol. the weather has been warming up here lately so ive starting driving with the windows down but i dont think that would make too much of a difference.

i heard somewhere that it might be some sensor in the tbi that went bad... do yall know what it might be and how much it would cost to get it replaced?

edit: im gonna change the fuel filter this weekend to see if that would help too.

 

[tRustyK5]

Might be a bad O2 sensor...

Rene

 

[durantk5]

it could also be a bad map sensor. mine went bad and kept fouling my plugs cause it was making it way too rich.

 

[suthrnchvyguy89]

Might be a bad O2 sensor...

i knew i was forgeting sumthin... yeah that got replaced about a month or two ago also.

what is a map sensor?

 

[big jimmy 91]

I have seen a plugged catalytic convertor cause a car to use more than double the fuel it used to.

 

[RustyMule]

Is the check engine light on?

 

[azblazer69]

I have seen a plugged catalytic convertor cause a car to use more than double the fuel it used to.

Yeah... That is what I was going to say too.

 

[suthrnchvyguy89]

crap i forgot to tell you that too... i have long tube headers and a true dual flowmaster exhaust without cats. and yes the check engine light does come on occasionally but when i took it to the shop awhile back, the guy said it was just because of the exhaust.

 

[RustyMule]

If you have a compy controlled truck, it needs an o2 sensor to tell the computer how it is running. If it/they have been diconnected, the compy throws a code and uses other sensors to "fill in the gaps" left by the missing signal. After a while it runs everything to its limit and the engine runs worse and worse. Go to a shop and have them check the codes. Then tell us what happens.

 

[cbbr]

Begin Hijack* Will a bad O2 sensor, along with the drop in MPG also cause the engine to miss or "stutter" at certain speeds. *Hijack Over

 

[RustyMule]

The o2 sensor is more of a "broad stroke" sensor. It tells the compy the state of things in the engine over time. If it is a specific rpm or speed, I would look into a bad MAP, TPS or speed sensor (if it has them).