HORRIBLE Gas Mileage

[dragon240sx]

Well I searched around and found some ideas but nothing that really helped in my specific case. For the past few months my gas mileage has dropped from 28ish to 18ish and I have no clue. Plugs are good, timing is right on, plug wires are good, brand new distributor cap...so I think I have the basics covered. The car's idle is fine and it's not losing any power either that I can tell but my gas mileage is terrible. Could this be a MAF issue (even if the idle is smooth?), how can I tell if it's a bad o2 sensor? I don't smell gas at any time during driving and I don't have any rotten-egg smell coming from the exhaust so I assume my cat-converter isn't causing any problems. The only thing bad on the car is my tachometer. It stopped working about 2 months ago...it just goes up and down whenever it feels like it so basically it has a mind of it's own, but I would think the tach is just a meter, it's recieving a signal but it isn't sending any signal out that would affect my gas mileage but I could be totally wrong...any ideas?

BTW, 1996 Nissan 240sx is what I have.

[bdeisle]

usally once the gas miliage starts goign to shit. then its the o2. but i wouldnt wait too long. i had it where my car will start sputtering and the fuel would start cutting out while i was driving.. it sucks

[Red]

I second the O2... Get it cleand or replace it... I had the same issue when I got my car.

[dragon240sx]

Now are we just talking about the first o2 sensor that is in the manifold or could the 2nd one be causing a problem too? Thanks!

[vltnolia]

just replace them both, wont cost you that much

[BadMoJo]

I get a steady 22mpg. Pretty shitty, but meh.

[mistaanime]

buy fuel injector cleaner. STP works fine..i use Lucas Fuel Injector cleaner...clean injectors every oil change.

[dragon240sx]

Yeah I used fuel injector cleaner and it didn't help a bit, that's when I started checking out other possibilities like the wires and distributor cap and all that stuff. Wow I checked priced for for o2 sensors and the Nissan OEM ones are the cheapest I've found online for $60. Everything bosch I saw was $64 for the one you had to splice and $69 for the one with the wiring harness on the end...I saw in a post some guy talking about $40, where the he** was that at?

[CustomS14A]

My aunts 89 had a small pin size hole on the fule line right from the tank

SO LOOK UNDER YOUR CAR

[TheSnail]

Its the O2 sensor, look for black smoke when you give the car some gas.

[gogeeta13]

o2 sensor is $16.99 from autozone, all you do is crimp one wire. easy as hell.

[hookedup240]

I get 20mpg of mixed highway and city driving, i don't think that's too bad.

[HyperTek]

I get crap millage and my car smells bad (according to the last time i got smog checked). Smog check is coming up anyways, so maybe Ill change mine too.

[twitchy]

aside from the O2 sensor, all in one day last year i did an air filter, plugs, fuel filter and oilchange. The bad o2 sensor prevailed but mileage did show improvement.

[tak-]

My car guzzles gas w/o the o2 sensor. But when i reconnect it, from 1k to 3.5k rpm, the engine jumps around alot, getting power spikes, then bogs down. bad sensor?

[Got Sileighty?]

wow talk about perfect timing. i think i need to check out my 02 sensors too. where would they be? yea yea yea noob question. i really oughta buy a FSM soon huh? :newbie:

[stumpz]

for some reason my sr gives me ~80 miles on 10 dollars of gas which is approx $1.79 a gal so that gives meh ~14.5 miles per gallon :-/ not that well..