Rich, then completely lean????????????

[duty780]

I have a 90" 240sx coupe, with a swapped 93" ka24de. the engine only has around 80 thousand miles. i Just recently did the timing chain, and the timing is at 20 degrees just to run safe. I have a cold air intake that goes all the way outside to where the bumper is, plus headers, and 2 1/4 straight pipe back. All this was great. My car, before i installed my air to fuel ratio gauge, idled from 650-850 rpm very slightly, never knew why until now. Now that i have the gauge it runs very rich at wide open throttle, and ok i guess at normal speeds. the problem is that after a while, about 10-15 minutes of driving, it goes completly lean, it actually disappears out of the gauge. i know is not the gauge reading it wrong because the car feels like crap and starts idleing very severly,i have to keep my a/c on so the rpm could chill out . i am not over heating because i have 2 electric fans running constantly. Nooooooooo is not my fuel pump, i tested it and i was running at 40-41 pounds.what in the world could it be ????????? any help would be greatly appreciated.

p.s once it runs lean, if i speed up around 60 70 mph it will start running rich again, until i start to slow down in which then it will slowly begin running completely lean again.

[Logan76]

Unless its a wideband gauge, it will either read completely lean or completely rich, the only thing narrow bands are really good for is idle afr's.

[duty780]

it is a wide band because it will sometimes read ideal and stay there for a while before going rich(when i hit the gas) or completely lean after the car warms up. if i let the car cool off for a while, it will be at good a/f ratio again. i have no idea what could be messing with my air/fuel ratio.I feel as if it only happens when the engine get to a sertain temp because it goes lean on the same red light when am on my way to school in the morning, and the same stretch of road when am on my way back home. is funny in a way but really confusing

[Logan76]

unless its giving you actual AFR's its most likely not a wideband, it sounds like your talking about a narrowband.

[duty780]

i dont know bro, is a cheap 50 dollar faze gauge, i just know it says completly lean, and the car smokes, engine shakes and idles like crap when it reads that.

[saejin]

i dont know bro, is a cheap 50 dollar faze gauge, i just know it says completly lean, and the car smokes, engine shakes and idles like crap when it reads that.

It does sound like a narrowband gauge, especially for 50 bucks. If it only says lean or rich, then it is narrowband. A wideband will actually have the AFR numbers displayed and cost over $200.

Also, how did you hook it up? Did you tap into the O2 sensor on the car. Is the O2 sensor still wired to your ECU or did you redirect the wiring to your gauge?

Any more info you can provide on how you installed it would help.

[Logan76]

If you wired the 02 sensor straight to the gauge and the 02 is no longer connected to your ECU that 's your problem, because the 02 sensor and MAF work together to get your idle and closed loop afr's, when your at wide open throttle and open loop your car is running 100% off your mafs reading's, thats why at WOT she runs fine but at idle and closed loops its not running correctly.

[duty780]

sorry i took a while to respond fellas, but i appreciate you guys trying to help. and yes i do have my a/f gauge tapped in , meaning yes it still goes back to the ecu. i did have a problem where i had to cut the o2 harness and re do it, my question now is, do the small wires that sorround the cable on the harness side need to be there? because when i cut it, i did not mess arround with that small layer of wires that soround the harness, i only connected the center cover one staright to the o2, and gauge wire. it seem that the slower i drive the longer it takes to start acting up. . i really want my baby to be in good health . please and sugestions will be appreciated.

p.s i have a super afc that i have not yet connected, will that solve the problem if i dyno tune it?

[duty780]

any body please

[saejin]

any body please

If you can post pics of what you did, that would be great.

I just installed my AEM wideband gauge and am getting weird readings, but my car runs fine, although a little rich at times. I had a second bung that I put my sensor in so I didn't have to cut any wires. I plan on buying a new oem o2 sensor today.

I'd hook the SAFC up and get some dyno time to tune it. A good shop should only charge about $75 and hour for the tune. Some even do flat rate of $250 and tune it until your happy.

Also, if it's really a wideband, then it will show the actual AFR numbers. Only the narrowbands have rich and lean labels. Post of pic of it and we'll know.

[gnomes321]

Well to me it sounds like as soon as your car gets out of open loop operation (after it warms up) the gauge may be drawing to much voltage from the ECU signal since it seems like you spliced it into the stock harness. That is return is causing your ECU to get an incorrect voltage from the O2 sensor that doesn't correspond to that of the MAF's. This could cause the car to run the way you described and throw the A/F off. If its a $50 gauge its probably a narrow band gauge, just remove it, its not doing any good. They are basically just a light show. If you really want to keep it get a second bung welded into the downpipe and and a separate O2 sensor for the gauge.

Anyone, feel free to correct me if I'm wrong.

[480sx]

Gnomes basically said what needs to happen.

The a/f gage you have in there is a narrow band, and it is COMPLETELY USELESS. He's right, its just a light show, you cant do a damned thing with it. Take it out, and sell it on ebay or something.

So was your car running well before you put the gage in? Common sense would tell you that if it was, then you messed something up in your install.

A narrowband o2 sensor is just for light throttle cruising. Basically it only has one function, to tell the ECU if the A/F ratio is perfectly stoich. Another way of saying it, the narrowband o2 sensor can only tell your ECU when your car is running as emissions friendly as possible.

PS- Your not boosted, your not making crazy types of HP, leave your timing alone dude. Set it back to stock, believe me, stock is safe enough.

[duty780]

Guys, thank you, the problem is fixed. Trust me everything that i had done was right, am not a dumba$$ AND 480SX, my timing IS set on stock. ok let me explain what fixed it which i never thought it would work but did. I was thinking and thinking and i came up whith the weird feeling that i needed some type of back pressure since i have headers, clean 2 1/4 pipe back with a megan racing tip. I figured my silencer would provide some type of back pressure. next thing you know, it does not lean out for anything anymore. i been driving it for 4 days and it is running "perfect" compared to what it was. my smoke is gone (except when i hit it because unfortunately it is running rich now). and guys trust me, that stupid little gauge works belive it or not, when am at a light and it goes to rich, you hear the engine changing sound, and as i said before, when it used to read lean, it would also act accordingly. am not saying is the best, but it works some what. give the preety light show a chance!!! thank you all for your help, i really appreciate it.