Nicelyphe

1993 S13
S13 Blacktop SR20DET
Stock stock stock..
Exhaust/FMIC/HKS SSQV BOV/WALBRO PUMP/z32 Fuel Filter/ NGK Iridium Plugs .030 gap
7lbs Stock wastegate

Alright my car has been burning through gas like crazy. A quarter and a half of gas within a 30 minute highway drive going a steady 60. Can literally just watch my gauge move haha.

There is no smell of gas inside/around the car. No black smoke. ECU throws no codes.

Could this just be a bad float? Could something else be pushing the car to burn through gas like this? Bad FPR, injectors, pump?

The ECU that came with the blacktop was a "62" that just recently fried. Now using a "63" since no one around here has a "62". Could this cause gas consumption issues? Some people say the 63 ECU has a diff fuel map vs. the 62, can someone verify that?

How to go about diagnosing this?

EDIT: Car also boosts too 9lbs. Also has just recently started.

Thank you.

andrew600

idk about ecu, but anything to do with a/f is obviously what you need to look at.
o2 sensors, mafs, iacv, fuel pump. thats just basic stuff.

someone should chime in with some help, hope you figure it out.

bussitcustoms

Are you ABSOLUTELY SURE it isnt leaking gas anywhere?

Nicelyphe

Sadly raining up here at the moment. I'm going to follow through all lines when I can. No smells of gas in or around the car anywhere. Will go check lift the fuel pump access door in a bit and visually check if there's any gas presence on them lines to/from the pump.

Nicelyphe

Yea, bit of diagnosing and it should all be right sometime haha. Getting my consult cable in a few days which should help. Sadly I don't have a wideband. Pumps about 11 months old or so, but who knows how long things last anymore..Was also thinking of possible o2 sensor, but I have no way to test and don't wanna go buying what I may not need as well.

fliprayzin240sx

Why dont you calculate you're actual gas mileage? Reset your odometer when you fill up your tank, calculate your gas mileage the next time you fill up your tank.

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Nicelyphe

I will do that on next fill up. I mean it may be nice to know an exact number, but this is def noticeable from previous times. I filled up last night, since then and now did about 45-50 miles highway and I'm at half a tank. That just seems way out of proportion considering I used to be able to drive ~30 miles and the gauge barely even moved =\. But if I don't figure out the issue by next fill up I'll keep you updated.

Nicelyphe

Also if I floor the pedal boost creeps to 9lbs, wastegate going? Its the internal stock t25 POS

JDMRIDDAZ

Leaky o ring or fuxed injector
Get that consult cable and run all posability down

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Corey121

I turbo'd my ka and i had a bad o2 sensor the wire was ripped and i got horrible gas milage if the sensors are the same then its like a 20 dollar part.

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marks14

Could be a vacuum issue also. If you say it suddenly boosts to 9 psi. Check for vaccum leaks just to be sure.

Croustibat

You can check your O2 sensor is working by unplugging it and see if there is a difference in the drive. But ECU has an error code for lambda not working so you should have seen it.

You might want to check what the ECU can do. I know for the CA the 44Fxx ECU does not have built in lambda control circuit, whereas 39Fxx does. You might have a similar problem.

Otherwise check for boost leak. But if it is going to 9psi it might not be that. Try cleaning your MAF too, that could help.

Not very suprised about boost going to 9psi if weather is cold, and/or if you installed a freeflowing exhaust / intake.

you could check the temp sensor too. If it is defective, the ECU will always command more gas. I dont have the values in mind, check the service manual for temp/ohm value .

Nicelyphe

Yea hopefully my consult cable will be here tomorrow. o2 wires are good, Getting power to the sensor and all that. Have not tried driving with an unplugged sensor. ECU throws no codes. Will check temp sensor, probably just replace it for the hell of it actually haha. Had my test pipe and hks hi power on for a year now and never had boost issues. It may be the weather, has been pretty cold over here in PA. I'll look around all vacuum lines once again and see if anything may be leaky again. Obtained a boost leak tester from a buddy, will check that aswell, but it hits 9lbs fairly easy so i doubt it has a problem holding boost. Car dont smoke or anything for that matter.

Biggest changes I've noticed in the past week/two weeks.

- Alot of gas going where?
- Boosts 9lbs on 7lb stock wastegate
- Popping from exhaust when down shifting gears.

Took out plugs yesterday, here's how they look.

Arireese

im also having the same problem..greddy intake, s15 turbo, and 3 inch ehxaust and walboro 255, 300zx ff..i get 150 miles to the tank. is that normal? oh and stock boost

Nicelyphe

GLad to hear I'm not the only one haha. No 150 miles to the tank is not normal, I used to get like 30 miles a gal highway..Till last week =\

Arireese

well im right here with you..haha. So far i've change my pump for another one, change my fuel filter to a new one, changed plugs. idk

Corey121

Have you done any upgrades to the car in the last week if so there might be a problem with one of the upgrades.

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spools420a

also keep in mind something as simple as a gas cap thats not sealing will let your gasoline evaporate,I had a bucket of gas outside and within about a week it was all evaporated,You may want to throw a fuel pressure guage on for about 10 minutes and see if pressure drops incase theres a little leak.

Nicelyphe

Actually sounds like a real good idea. About to look into heading to the auto parts store after work and pick something up, sr fuel pressures like 38 or 40 or so?

DaveAZ

Pressure in the gas tank? Certainly it's not going to hold return feed pressure after shut down. But as another fuel economy sufferer with no apparent reason, you may be on to something.

What should the drop be? We have a gauge and it goes way down after shutdown, eventually zero.

Nicelyphe

Yea, I havent changed pump, mainly cause its only like 8-11 months old..changed filter, re gapped and checked plugs.

I am running a 63 ECU on my blacktop. Thinking of getting an E5 ECU and trying that, but shouldnt make my gas mileage that bad cause all last year I ran a 62 ECU and got great gas mileage. Unless my o2 sensor is shot, sadly no good way to test these things.

Arireese

i get a check engine when i shut the car off. but i cant pull codes cause the plastic screw in my ecu is stripped.. :/

Nicelyphe

Shit that's no good =\. I dont get a light but I dont think my dash light is wired up. I checked codes, all are clear. Ima reset my mileage counter when I refill next and see what I pull per gal

DaveAZ

Looking at those plugs, man those are clean. Too clean. Are all of your plugs like that? I can't tell you where your fuel is going, but it sure isn't going through the engine.

With an "iffy" O2 sensor, we burned rich. Changed it out for the heck of it, and we definitely got a better running engine, though minimal gains in fuel economy. The one plug we found that looked like yours was due to a faulty injector. Caused it to run rich on the other three, but we could smell the rich fuel.

In your case, I'd look for boost or vacuum leaks as said above. Maybe leaking out the BOV? Something else we did was to get an adjustable FPR and pressure gauge. I played with that, and different pressures made a lot of difference in how it ran with the stock injectors, 255 pump, and T28 turbo.

Nicelyphe

Yea these plugs have been in the motor for a year or so. All 4 look EXACTLY like this. I'm thinking of just changing the o2 sensor and seeing if it helps. But yea by the look of the plugs, def not rich conditions. Someone did tell me they look like a little bit of pre detonation going on though. I'm going to pressure test and see how that goes. Yea I've been skipping out on buying a adjustable fpr and gauge haha, should really get on that >_<.

Arireese

damnit..should i just replace my gas cap? I have a sick one from a silvia. lol.

Nicelyphe

Isnt the pressure supposed go down after shut down? Then it just re-pressurizes when you turn the key?

Nicelyphe

Fuel pressure gauge installed! 42PSI When IGN turned on. When car is off pressure slowly drops, about 1psi per 10 secs or so? Anything of concern?

cotbu

I hate Iridium plugs, they burn through anything, gas, oil and water. So use coppers gaped to .028in. Check your oil. Also I've done tunes that idle 13.5afr and cruise is still 14.7-15.2, with a working 02sensor. Post your consult logs. Have you looked to see if the ecu is chipped. Not Feeling Halftime!

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Nicelyphe

Haha nice. COnsult cable is still on its way been waiting about 3-4 weeks now..I should get a wideband so I can see afr under throttle and what not. Still debating on using some coppers also. ECU is not chipped, its actually a 63 rather than a E5. But I've heard that wont make a difference.