S13- SR- Gas going fast!

[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]

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.

[Nicelyphe]

Are you ABSOLUTELY SURE it isnt leaking gas anywhere?


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.

[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.

[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

[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.

[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.

http://i235.photobucket.com/albums/ee97/B0RN2KILL200/6a50f0ee.jpg

http://i235.photobucket.com/albums/ee97/B0RN2KILL200/2e9c9e41.jpg

[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]

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 =\

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 :(

[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]

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.

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 >_<.

[Corey121]

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 =\

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

[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]

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.


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]

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.

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.

[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!

[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.

[Boost_Fiend]

^^^ It will make a difference depending on your o2. I bet its your ecu - o2 combo. You have a black top so you should be running a "fat" o2 and you are running a 63 (redtop) ecu. You will need to swap your o2 sensor for a "skinny" redtop o2. I had the same problem and was using a skinny o2 with a e5 ecu. My wideband would read 11.00 at cruising and idle.

[Nicelyphe]

Yea I've heard so many different answers on things like this, I am running a FAT o2, I think im going to just get a E5 ECU. Considering a conversion bung + skinny will equal the same cost.

[Boost_Fiend]

Yea I've heard so many different answers on things like this, I am running a FAT o2, I think im going to just get a E5 ECU. Considering a conversion bung + skinny will equal the same cost.

There is your problem. Try running w/o an o2 until you can get the right parts.

[EnemyS15]

The problem is you have zomg bad ass motor brah! You need a motec !

[Nicelyphe]

Lmao wtf ^

[DaveAZ]

There is your problem. Try running w/o an o2 until you can get the right parts.

Lots of conversations over the years on this subject. We're running a "fat" O2sensor from a 300ZX TT in a Red Top stock ECU.

In this application, the fat O2 sensor actually is titania as the Red Top ECU was designed to use.

Black Tops use the zirconia type of O2 sensor.

From what I am finding, "fat or skinny" don't necessarily denote which type of sensor it is. Interesting. Going to have to check ECU number and cross reference, then check sensor voltage. (or toss in a bung and skinny?) Smells rich to me, and MPG sucks. Might have fuqed this one up.

Nicelyphe, if you have a Black Top ECU, those O2 comments make sense. Did you ever try the gas cap deal? Also, did you get a chance to compute your MPG?

[Nicelyphe]

MPG I do a bunch of high + mixed city driving during a weeks time, and i last put gas in and forgot to reset/monitor my odometer..I could attempt to purchase a new cap and see if it helps.

I don't have a Blacktop ECU at the moment, but thinking of getting one too see if it helps at all. It's kind of a hit or miss kind of deal though.

[Nicelyphe]

Consult cable should be here after work I hope! Anyone know of real good monitering programs? I have a couple on my computer, but forget the names. The cable is also coming with TECU.

I'm on the look out for an E5 ECU as well.

Also what too look out for to stop my boost creep to go to 9lbs rather than the original 7?

[Croustibat]

Exhaust/FMIC = higher boost than stock. Nothing you can do about it.

Make sure the CAS is set properly, then get your car mapped. Nothing else to do ...

try checking engine temp sensor, ECU diagnostic does not always detect it failed when it is, but this will cause the ECU to enrich all the time.

[Nicelyphe]

Just checked timing and such last night, was jumping between 15/20 degrees, adjusted that. Next may be temp sensor replace for the hell of it.

[Croustibat]

Make sure you set/check timing with the car hot and at idle, because the ECU changes timing when it is not. Base is supposed to be at 15° exactly, not jumping.
If it is jumping, it could be a temp sensor failure, a CAS failure, a TPS switch failure (if it does not detect idle, it does not switch to the idle timing map) ... or a wiring problem. I honestly dont think it is the TPS, as timing map is above 20° value near idle. But if it is lambda sensor issue, it could interfere too ...

I hope it is the temp sensor or the lambda, all others are costy repairs. Even the temp sensor is costy, i think it is 60€ + here. But seeing as a CAS is 200€+ ...

Cas is driven by the exhaust camshaft, the splines on the cas or the part driving it can wear. I think JWT has a replacement part for the splines on the camshaft. It usually is changed in pair, because, as soon as one of them develops wear and play, it starts grinding the other part.

[Nicelyphe]

I see. Yea yesterday I did it Hot and at idle, but I never disconnected the tps. So tonight I think ima disconnect the tps and do it again >_<. It was jumping last night until I adjusted the CAS. My idle is around 800-850 depending on draw. My electric fan makes my idle drop and my headlights make my idle drop when on, so at night that two current draws.

[Croustibat]

You can set idle higher the time needed to set timing, the ECU keeps commanding 15° until you go past 2000~2200rpm (AND if tps switch detects throttle closed). Not sure disconnecting the TPS is a good idea, it may send it to limp mode. You can check your tps switch is working, if memory serves it uses a switch to "see" idle , and a potentiometer to check throttle opening. I dont remember the values but it should be pretty easy to check if the resistor value changes when manually opening the throttle. Same goes for the switch. Do this check when engine is off, no contact, you dont want power there as you are checking for resistance.

[nassin31spr]

I have a sr20det with a blacktop fat o2 and both a red top and e5 ecu. I've noticed no difference. Still gets bad gas mileage. I'm going to reseal my gas tank and get a new cap next because I beleive it may actually be evaporating my gas cause when I go to gas up there's no pressure in the tank. Also going to t off the boost guage somewheres else so the Frp has no interference.

[Nicelyphe]

^^ Actually I've noticed I no longer get pressure out of the tank when getting gas either and I used too...Maybe my cap is an issue >_<. Also I want to run my fpr separete from my gauge as well, but I dont have a spot to put the gauge besides there =\..Any ideas on a diff location?

[Boost_Fiend]

^^ have you tired running without the o2. This helped made my car run much better until I was able to get the correct o2 (I just went to advanced and got one for a 300zx). I have emanage though. W/o the o2 I believe the motor should stay in open loop. give it a shot.

[Nicelyphe]

I have disconnected while in idle[Made no change], I have not drove without it disconnected. I may attemp that and see how it acts.

[Boost_Fiend]

Do you know for sure nothing changed. I don't recall you mentioning that you had a wideband,or anything to minute afr

[Nicelyphe]

Well in that sence no, I do not have the equipment to moniter afr =\. I meant more or so sound/idle performance. Was thinking of picking up a wideband tbh. Would probably help my situation alot. I'll be messing with consult tonight and see if I can actually get any good values of anything.

[Boost_Fiend]

Yeah... you should probably invest in a wideband and remember the motor is going to run pretty rich on,a cold start

[Nicelyphe]

Yea I have a buddy locally trying to sell one. Is consult able to give me accurate afr? Are you familiar with consult readings?

[Boost_Fiend]

Not really. Imo the best wideband is the PLX. But I am using the AEM uego and it seems pretty accurate.

[Nicelyphe]

I see, I'd more or so be going with the AEM as well haha

[Nicelyphe]

Actually got to play with consult a little bit..It looses connection to the ecu after about 5 secs of diagnosing :( But here's a little something..My o2 sensor has 0 volts.
http://i235.photobucket.com/albums/ee97/B0RN2KILL200/64e7e3c9.jpg
http://i235.photobucket.com/albums/ee97/B0RN2KILL200/50a3d962.jpg

[nassin31spr]

^^ Actually I've noticed I no longer get pressure out of the tank when getting gas either and I used too...Maybe my cap is an issue >_<. Also I want to run my fpr separete from my gauge as well, but I dont have a spot to put the gauge besides there =\..Any ideas on a diff location?

Frsport sells a easy vacuum tap. You just drill a hole and put it anywheres. I have mine on the turbo hotpipe elbow and ran the hose to the wastegate. It makes for a much cleaner look without the hose running across the bay.

[Nicelyphe]

Ah yea I have one of those, I got my wastegate going too it actually.

[Boost_Fiend]

Your o2 could be wired wrong or the ecu is not recognizing the o2 because it is the wrong one. A brand new o2 at autozone is only like $60, you should have bought one already.

[Nicelyphe]

Yea, I'm skipping the o2 conversion, and just going to go source an E5 ECU since my harness is from a blacktop, and I'm running blacktop everything else either way. I've had about 3 people on here offer to sell me an ECU, then never get back to me..Know anyone?

Also, I did just see that thread with the other kids thread with the o2 issue haha.

[Boost_Fiend]

^^ yeah that thread helped me alot. i've been scratching my head over this issue for over a year. if you want i can send you my old skinny o2. i have no use for it. im pretty sure the the harness's on the s13 sr's are exactly the same. could be wrong tho.

[nassin31spr]

Harness plug for tge o2 is diffrent. I just put my e5 back on my blacktop swap and have noticed no difference. I switched my boost guage vacuum tonight. I'll let you know if it makes a difference. But the ecu did nothing.

[Boost_Fiend]

^^ are you sure about that? I have a redtop with a "redtop harness" and am currently using a "fat" black top o2 with a e5 ecu. I did nothing but take out my skinny o2 and put the fat o2 in. do you have a wideband to actually know if there is no difference? because as soon as i put the correct o2 in to match the e5 ecu my afr's were much different, no longer rich all the time, and maintained a stable 14.7 at cruise and 13.5 at idle. maybe your rich problems stem from else where.

[Nicelyphe]

^^ yeah that thread helped me alot. i've been scratching my head over this issue for over a year. if you want i can send you my old skinny o2. i have no use for it. im pretty sure the the harness's on the s13 sr's are exactly the same. could be wrong tho.


It's cool, I dont wanna mess with either putting a 2nd bung in my elbow, or buying that dam adapter to go from fat to skinny =\. Maybe nassin31spr will sell me that E5 :bash:

[Croustibat]

Yea I have a buddy locally trying to sell one. Is consult able to give me accurate afr? Are you familiar with consult readings?

no, consult will give you oem narrowband afr data, which is useless if you are not a computer. It can only say "lean" or "rich" as basically it outputs a signal between 0.2 and 0.8V. That is enough to make a fine adjustment, like in a closed loop system used in a car, but no good for tuning. A wideband lambda sensor outputs a 0-5V signal which gives you a very accurate result. It really is very useful, not only for tuning, but it helps see when things go wrong. The problem is you usually need to have a bung welded on your downpipe to install it . I am using a PLX one too, but would have went VEMS if i could at the time i bought it... Nearly all wideband kits use a bosch LSU 4.x sensor. the VEMS system is "better" because it has AFR and EGT on the same gauge, so that is 1 less gauge on the dashboard :D

Imho you have a wiring problem or a dead sensor. Can you try wiring it yourself ? A narrowband sensor is not that difficult.

[Nicelyphe]

no, consult will give you oem narrowband afr data, which is useless if you are not a computer. It can only say "lean" or "rich" as basically it outputs a signal between 0.2 and 0.8V. That is enough to make a fine adjustment, like in a closed loop system used in a car, but no good for tuning. A wideband lambda sensor outputs a 0-5V signal which gives you a very accurate result. It really is very useful, not only for tuning, but it helps see when things go wrong. The problem is you usually need to have a bung welded on your downpipe to install it . I am using a PLX one too, but would have went VEMS if i could at the time i bought it... Nearly all wideband kits use a bosch LSU 4.x sensor. the VEMS system is "better" because it has AFR and EGT on the same gauge, so that is 1 less gauge on the dashboard :D

Imho you have a wiring problem or a dead sensor. Can you try wiring it yourself ? A narrowband sensor is not that difficult.


This weekend I'm going to track back through the harness and check through the wires.

[Nicelyphe]

Checked harness wires, everything looks good, the o2 sensor gets 12v at the plug. I've been driving with the o2 sensor unplugged now and it drives and runs the same way if plugged in or not plugged in. Guessing it's a bad sensor and I'll most likely be going this week to grab one.