S13 getting 8 Mpg highway

[Skynet]

I have a 1990 s13 with a fully stock ka24e that currently gets about 8 miles to the gallon highway. I've replaced the fuel pump, fuel filter, done 2 different full tune ups since this started happening. Swapping a blacktop in soon, but it's still my daily until then so I'd like to fix it if at all possible. I'm assuming it's some type of an injector malfunction, even though when I pulled the ecu, there were no codes at all. Car does seem to run rich, I just recently put on a new exhaust and within a week the tips were coated in thick black sut. Any ideas would help a ton, so thanks in advance.

[Kallixtos]

Hard to start when cold? Maybe leaky fuel injector?

[PPman]

Check your MAF clean it, open it to make sure the contact leads between the circuit board and the connector are actually touching and not corroded) clean it real good if the connectors are missing broken, solder them or if need to be replace them with wire and solder it, check your knock sensor, vacuum leaks, check your timing, check your EGR valve, and all the emissions crap. After that clean your plugs because more than likely they are fouled by now, no need to buy new just clean them with fine sand paper.

[Skynet]

I've already cleaned the maf and fixed any obvious vacuum leaks, I forgot to mention that in my original post.
But when I checked, the maf wires seemed fine, but I'll check again. What are some signs of a leaky injector?

[ultimateirving]

I've already cleaned the maf and fixed any obvious vacuum leaks, I forgot to mention that in my original post.
But when I checked, the maf wires seemed fine, but I'll check again. What are some signs of a leaky injector?

leaky fuel lines or Fuel return leaks or similar? 8mpg is pretty retarded and if its running that rich i feel it would struggle to drive,

[PPman]

I literally meant open it as in take it apart. The contacts I referred to are inside the maf and sometimes they get corroded or fall apart.

Sent from my Galaxy Nexus using Tapatalk

[!Zar!]

How are you calculating your gas mileage?

Are you sure your gas gauge is accurate?

How many gallons go into the tank when you fill up?

Have you tried carrying around extra gas and seeing exactly how long you can drive before you are truly out of gas?

[Skynet]

Yeah, it's 11 gallons from Empty every time, so nits actually using the gas. And the cluster was brand new, and I've replaced it with a jam cluster since i bought it.

[zerodameaon]

I suggest you check your speed with a GPS. Cluster can be working 100% but tire size and your speed sensor play the larger roll with how far off your calculations are. Also whats a jam cluster?

Also your gas gauge is way off if you are at empty and only putting in 11 gallons, our tanks are 16 gallons. Even with two large dents I can fit 15 gallons in my tank from bone dry.

[!Zar!]

Carry a couple gallons in a gas jug.

Fill tank up and reset tripometer.

Drive car till tank is empty.

Record distance.

Fill car up with gas jug.

Drive to gas station.

Report back here with your findings.

[Hashiriya415]

What do your plugs look like??

http://4.bp.blogspot.com/-j0zzs4Ml8NE/TgNu2KPVUAI/AAAAAAAACt8/Z--jY0NwoDs/s640/Spark+Plug+Reading.jpg

[e1_griego]

Coolant temp sensor and/or o2 sensor issues are common KA failures and will cause lots of richness issues.

If you didn't address those in your tune-ups than they could be the culprit.

[Skynet]

Really, 16 gallons? I thought the s13 had a 12 gallon tank?
Jam=autocorrected jdm cluster lol
I'll swap out o2 sensor tomorrow at work and see what that does.
The cluster dropped at the same ridiculous speed before I swapped to the jdm one though, and it still reads the exact same. Possibly a tank float problem?
And the plugs are less than a week old, but the plugs I pulled out of it were definitely fouling.
Also, stock wheel and tire setup, only modifications to the car are suspension mods. Coilovers, power brace, etc

[robinsone]

fuels lines, replace them, all the rubber, from the hard lines in the engine bay, where i've had leaks. But don't forget about the fuel lines from the hard lines in the back to the top of the fuel pump. The rubber hoses aren't supposed to last more than 20 years. I've had bad leaks from both spots, replace all the rubber fuel lines period, its too easy not to do it.

[zerodameaon]

Good chance that your tank float is bad or the contacts are dirty if both clusters read the same. For your mileage are you converting from km to miles since you have a Japanese cluster? Also are your tires larger then stock?

[Skynet]

Hm, what contacts are you meaning?
And yeah, it would be 3.4 km/l, so around 8.3mpg
Will also change all of my rubber lines, i work at an advance auto so I can get the stuff for free or cheap. how would I check to see if the float is bad though? the gauge does read pretty sporadically from time to time.
And wheel and tires are all stock size/offset/everything
so In the morning I'll change:
02 sensor, vac leaks if any, which I dont think there are, fuel lines, and possibly injector o rings if we have them in stock for a ka24e

If i were leaking gas somewhere, from the injectors or from a line, i would be able to smell raw fuel correct? because as of now I do not, and the car runs fairly decently

[DJ-of-E]

I'm still trying to figure out how the hell at 8.3MPG on a KA24DE. I track my 240sx and hit the redlines alot and the lowest I go is 15MPG. 8.3MPG is seriously dumping to the point where the car is very hard to idle correctly.

Is the cluster tell you how much MPG you're running or are you calculating this yourself? I mean, it sounds like you'll run out of gas or go empty after barely 100 miles.v


Carry a couple gallons in a gas jug.

Fill tank up and reset tripometer.

Drive car till tank is empty.

Record distance.

Fill car up with gas jug.

Drive to gas station.

Report back here with your findings.

[Skynet]

yeah, I work 30 miles away from my house, so if I drive there I'm at almost half a tank if I start at full. the drive is all highway, no city. I don't drive like an ass either, so that wouldn't be it. lol
but yeah, its really that bad. I mean even if the cluster is off, after driving 30 miles I shouldn't be able to put 7 gallons of gas into my tank, which means the fuel is going somewhere. the question is, where.

[zerodameaon]

What does your exhaust smell like? If its that bad you should be almost dumping gas out the tail pipe and smell it if you walk around the back of the car. If you want to check for gas leaks set the car on a level clean surface and start it up and just let it run, you should see drips if you are leaking.

[Skynet]

The exhaust is definitely rich, but there's no liquid fuel coming out. car does backfire on its own quite alot when downshifting though, if that means anything.
Also, I've tried watching it run, and I see no fuel leaking to the ground, nor do i see any around the fuel injectors

[yetijeff]

Is your emissions stuff still intact and working? If ur egr system is clogged and/or not functioning it could cause u to run rich. Although 8.3 mpg is insane there's gotta be a leak. My car runs rough with a fucked up egr system and I still get 16-17 mpg driving like an asshole on 91 octane...

[zerodameaon]

Real quick you are using this conversion, 1.60934km to 1mi right?

[Skynet]

Emissions is still in tact besides the intake resonator. and I have no idea, I used an online generator for the conversion so I assumed that was correct. Why?

[!Zar!]

Maybe Swiper is syphoning your gas.
http://images2.wikia.nocookie.net/__cb20120525190252/uncyclopedia/images/4/4d/Swiper.gif

[yetijeff]

Emissions is still in tact besides the intake resonator. and I have no idea, I used an online generator for the conversion so I assumed that was correct. Why?

But is it working? Do u have a cel?

[Skynet]

I imagine so, I've not checked that but I'll look tomorrow for clogging.
And nobody is stealing my gas, since it's only happening while I'm driving the car. or else that's a really dedicated gas thief, and he deserves that gas. Lol

[yetijeff]

Check clogging and also see it the egr valve itself is actuating. Easiest way to tell is reach ur hand back there and feel in one of the holes in the side and see if the diaphragm is moving at all when u give it gas.

[DJ-of-E]

I still think you're leaking pretty badly somewhere rather than burning rich.

8.3MPG at below 3,000 RPM means you're running a high right air fuel ration where you shouldn't be able to drive to begin with. Your intake shouldn't even dump enough air properly.

[Slippin'eight-nine]

You must have a fuel leak somewhere. There is no way your car wouldnt be barely running or running like complete shit averaging 8 mpgs. Like some else said, they pound it and still manage around 15.

[Def]

8 mpg does point to a leak, as that's the kind of mileage I'd get on track with a ~350 rwhp SR20DET (7-8 mpg).



Does the car smell like raw fuel?

I'm also thinking fuel line leaking, as a steady drip would definitely give you around that, and I've had it happen to me on original lines.

I'd also check injector o-rings or an injector that's stuck open. Pull the rail, turn the key on but don't crank. You should see no leaks while the rail gets to pressure. Then have someone crank it over with the coil disconnected while you watch a few sprays and make sure they spray and don't dribble all over the place.

[Skynet]

will definitely do that today with the rail, and possibly the o-rings as well. Where should I check the fuel lines for leaks?
Thanks for this thread by the way, this has been a ton of help since gas is 3.45 here in Louisville right now, hahaha

[Slippin'eight-nine]

Ive had just about every type of fuel leak imaginable. The actual filler neck and rubber sleeve running to the tank. If I filled the car Full it would leak out to 3/4 tank.
Ive had the rubber lines coming off the tank going to the hardlines leak. It was a steady drip. I couldnt tell cause I parked in the grass and gas evaporates.
Ive also had the fuel injectors leak from the injector body rather than the orings.
My car used to reek and I would be high as a kite upon reaching my destination. Haha!
Keep in mind these were all at different times over the course of several years.
Good luck and keep searching