GAS GUZZLER!!

[95nismo240]

well my car was just rebuilt (head and block). before it was rebuilt it wasted alot of gas i only got like 50 miles to a quarter tank. when i got my car back it still had the same gas milage. my check engine light was on before and after i had my engine rebuilt but i never checked the codes my self. i just checked my codes today and the ecu threw out code 103 (Park/neutral Postition Switch), code111(Inhibitor Switch), and code125(Line Pressure S/V). i have no idea what this means, but i think the code 111 and 125 if for my transmission. i have no problems with my transmission whatsoever, it shifts perfect and all. i try to get codes for ModeII (Engine ON)- Exhaust Gas Sensor Monitor) to see if my o2 sensors are fried because thats what i thought was causing my bad gas milage. but the check engine light just blinked and blinked. it didnt pause or nothing so i dont know what codes it threw out. sorry for the long post and plz post any ideas on why u think my car is wasting so much gas.

[95nismo240]

BUMP. anyone??

[onosqv]

Well, I believe when something goes wrong, the ecu switches to a fail-safe mode, which obviously wastes gas.

Um, since you rebuilt the engine, I'm guessing you also did a tune up (i.e. plugs/wires, dist cap, rotors, o2 sensors, checked coolant sensors/switch).

Did you also have your injectors checked, make sure nothing is leaking?

And this is really stupid but: properly inflated tires?

Also there's similar threads about crappy gas mileage, those should give you a pointer.

Lastly, try resetting the ecu (still has saved info from old engine probably) and give it a week to adjust to the new engine (they remember last 50 start ups & driving patterns or somewhere around there)

[95nismo240]

yea i reset my ecu and my check engine light went off for about 5 miles then all of a sudden it turned back on. i have changed everything except for the o2 sensors. im hoping that they are the problem.

[onosqv]

here's what I would try:

don't "bolt" the ecu back in, but leave it kinda dangling. reset the ecu. drive, then as soon as the light comes on, pull over and check the codes.

Then whatever codes you get, post in the Mechanics section - cuz if you get those 103/125 errors, I've never had those or have read of ppl getting those, so I have no clue how to fix those thingies.

Have you figured out the mpg you get? fill up. reset odometer. drive around for a week or however takes you most of tank, fill up again & calculate.

O yea, your not smelling funny injected "gas smell" in the engine bay, interior, or from the exhaust are you?

[95nismo240]

i know i get about 100 miles on a half a tank of gas. so around 200 a tank. thats if im under 3k rpms the whole time. ill try reading the codes again tomorrow. ill drive it and when it turns on ill read them. but im pretty sure it will throw out the same codes. i noticed if u are looking at my transmission from the front, on the left side where there is an electrical connector, there is a whole bunch of wires that were spliced and they are now connected back together with plastic pieces between the wires. maube thats why its throwing out those transmission codes??

[iPrecisionNET]

I'm running an auto 97 with under 100k on the odo. I have always had crap gas mileage in the 240, it's something I've learned to accept. It would be really helpful to the suspicious if we made some sort of submittal where everyone with a certain mileage s14 did a gas mileage submission. Draw the tank until the empty light comes on and then press the odo reset, then fill up the tank (and write down the exact number of gallons put in) and run it again until it hits the empty light. it wouldnt be 100% accurate but probably close enough for people to compare with eachother to see if theyre in the norm or not. I'm up for this test, I run mid grade (89) curently and the car is back in stock form with auto trans and 195 tires.

[onosqv]

Yea, we've done something similar w/ the older threads where people were comparing why some had such crap mileage and some had great mileage.

I've calculated mine over the past year (w/ an s13 w/ about 160k mi) I don't have the exact fill ups, but I did my math closest to the gallon rounded down

Stock: about 22-23mi/gal on 91 octane running 205/40R17 tires

Intake/Header/hi-flow cat/exhaust + pulley: about 20-21 mi/gal on 91 octane, same tires, about 18-19 on 89 octane - this may have been due to my more prone to revving and lead footing bcs of better flow/sound/speed.

Above + 100 +/- lbs in audio equipment, new paint job, 2 batteries instead of 1: 17mi/gal (if I'm lucky) on 89 and 91 octane on 18" rims - think tires are 225/40 or somewhere around there.