horrible gas mileage

[mordakibojangles]

(89 240sx) I recently changed the spark plugs and wires distributor cap rotor o2 sensor fuel filter and an oil change and im only getting 15 mpg. I dont drive the car hard and i do about 50/50 driving.

[alms24sebring]

hmm.. any check engine lights? Burning oil? Check for any broken vacuum lines. Also if your using anything but 87 octane, mpg will decrease.

[mordakibojangles]

My check engine light isnt on. the oil is still at the level its been since i changed the oil a week ago. No broken vacume lines either. i am running 91 octane i heard it was better for it

[alms24sebring]

Bingo. Its not really better for it if it doesnt require it. Its meant for higher compression and higher hp cars so the car doesnt knock. When you run a higher octane in your car, you have lots of unburned fuel leaving the exhaust. The injectors will fire more fuel for the same amount of power that you get from an 87 octane. Go back to 87.

http://www.nicoclub.com/archives/gasoli ... myths.html

[mordakibojangles]

that would make that big of a difference

[alms24sebring]

Yes it does as you see. I was running 89 for the longest time in my S14 and would get maybe barely over 300/tank (21mpg) when I babied it and it was 65% highway. Then I learned.. went back to 87 and I was getting closer to 350/tank like it should be (about 25mpg). And, you'll be saving lots of money from not wasting more expensive fuel. Higher octane does not mean a better burn or quality.

[mordakibojangles]

just wondering could there be any other problem

[alms24sebring]

This is the easiest way to see. It costs nothing, in fact you save money. Run the tank to the E and fill it with 87. If the mpg goes up to normal, you owe $50.

[mordakibojangles]

yea i pobably only gained a half a mpg and that was while tryin to baby it as much as possible also it seems like it jus drinks gas on the highway

[BusyBadger]

It's hard to say without a lot more info on your part, but my money says bad injector.

[alms24sebring]

wow thats hard to say because the only other thing I can think of is your temp sensor for the computer is always reading cold, letting dump alot more fuel in all the time. I was positive it was the octane, 87 -> 91 is probly atleast a 5 mpg difference.

[mordakibojangles]

would the gauge on my dash still work if the temp sensor is out

[alms24sebring]

Theres one for the the gauge and one for the computer. They are right next to each other but I dont know if they have the same specs. Its like $3, worth a try. Let me see if I can find a pic. Are you seeing black smoke out the tailpipe while driving?

[alms24sebring]

1991-1994-240sx-coolant-temperature-sen ... 54375.html

[S13_RB25]

Did you gap the plugs? I know they say that the plugs are pre-gapped but i don't think there not within the 240 specs. IIRC the s13 specs are from .39 - .43, so make sure the plug gap is right too. I know it won't make a big difference but it'll help.

[mordakibojangles]

no black smoke coming out but i did just check my air filter and the bottom 1/3 of the air filter is black and wet and i jus replaced it a week ago

[alms24sebring]

hmm. weird. ummm.. if your missing a splash shield and the lower part of the airboz you could be getting water in there?? That still doesnt make since to me though

[mordakibojangles]

theres a box with a hose that runs to my air box when i looked into the hose the seemed to be moisture in it also i just bought a coolant temp sensor gonna replace after the car cools down

[alms24sebring]

aight. Put teflon on it too or itll leak. You shouldnt need to bleed it either

[mordakibojangles]

any clue on why there would be moisture coming from the hose going to the air box

[ricebike]

any clue on why there would be moisture coming from the hose going to the air box

yea the AIV reed-check valves are not closing fully;

here's a quick fix:

post6270188.html#p6270188

so, the exhaust is basically contaminating your air filter & you're not getting enough oxygen to the combustion chamber

[alms24sebring]

I would have never guessed that. I dont know S13s very well . But keep using 87 Im telling you

[mordakibojangles]

yea i still aint havin no luck i replaced the coolant temp sensor adjusted the timing because i found out it was still out by 5 degrees and ive been using 87 octane and all i manged to get is up to 17 mpg anymore help would be apreciated

[OutToWinPAHC]

Let off the gas?

[LoserCard]

Check your timing?

[alms24sebring]

Let off the gas?

lol This is like seriously the only other option. Did you fix the air injection thing as posted?