chk engine lite on, MPG goes down drastic, any idea?

[calicelica]

My engine light turned on as I was driving on the freeway. How to check for codes? The only thing obvious is that my fuel economy rate is not so economical any longer...I always warmed up before driving ussually way down to 750 rev. Could it be my intake sensor? or fuel management? The car runs just fine, but I'd love to keep my 30 mpg...any ideas??

[LaYzIeNoY]

imma throw out an idea O2 sensor

[91 Celica St]

does it also fell a slitght loss of power?
my stuf does that cuz i throw distributor caps about every 10,000 miles, my ideal drops to abotu 700 gas mielage goes to shit and loss of power and cel's wont come on for about another 5k...pull it off and check to see if theres anycarbon buildup on the points, f there is, change it

[calicelica]

Barely any loss of power, well @ least if any I didnt really notice... I actually just changed the distributor cap and rotors just about 5 months ago. So far, I've driven about 7000 miles since. What did u mean by throwing dist. cap every 10,000? you changed it or just cleaned it up? is that the standard? As far as O2 sensor, why would that be? I'll change both if necessary, but since sensor is more pricey, how do I make sure that it is not working properly? Thanks a lot guys!~
BTW, my uncle said something about my car won't be able to pass emmission or sumthing...Im not sure how the hell he came up w/ that, but does a broken O2 sensor messes up exhaust/catalytic function?

[LaYzIeNoY]

a messed up O2 sensor would throw of the a/f mixture or could

that would account for bad mpg and the light

uh i ferget how to check it, i mean i don't even know if it is a problem or not, it was just a suggestion, does anyone on here know a way to cehck i bad o2 sensor

[91 Celica St]

no real way except to see if its reciveing and sending the right amount of voltage, look in your chiltons manual it should say the voltage of reading

i believe its 7 recieve and 4~5 send, any less or more on the send then its bad


and yes, misfiereing/dentonation/ and loss of gas mielage is a pretty srue way to make you fail smog due the the combustion process being bad

[CelicaGirl]

intake could make you lose gas mileage in the cold weather. I noticed the same thing with my car when I was getting like 400 miles per tank and now I'm getting about 350. My friend explained it to me...but you don't want me to try to explain it to you I'm sure. If you want a cheap code reader buy one from harbor freight or you can go to autozone and have them hook it up for free.

[calicelica]

okay, thx a lot. Ill try to check it w/ a voltmeter...I haven't seen it a the manual since I forgot where the last time I put it. Thx for code reader info, - mb you're right about intake...makes sense...the sensor got real cold, but that shoudnt take so much of gas... even when I tried the cheap temp. resistor a while ago, gas consumption wasnt too bad. aneway, gratzie.

[91 Celica St]

wait are u thorwing check engine lights? if you are its probably your o2 sensor or something with the intake stream (maf mabe) youll never know unless you diagnose, see what it tells you, most liekly too rich/too lean codes, i think its 13

[calicelica]

I dont know man, its been really weird! last time, I was driving 8 hours straight around LA, the consumption was so economical... and then the night after I only went one way to hollywood and its was aobut 2 gallons for 25 miles... anyway, I was pretty sure about the O2 sensor also, still haven't checked it, no time, but will do tommorow.