Help...Getting 13 MPG with my Ka24de s13

[240sxOwner]

I have cleaned mass air, put in 2 new o2 sensors, new ngk plugs, and new nkg wires...

Afetr all of this my air fuel gauge still reading Very Very Lean, .03 volts from o2 sensor. Is the computer trying to correct for "running lean" therefor dumping fuel into mix? I am gettign a reading of .03 volts from the connector of the o2 sensor even with my multimeter. I need Help

[frapjap]

Try posting in Nissan Online Mechanic. Those guys are wonderworkers!

[deeznuttz2]

should'nt u be running rich then...if it's 13mpg?

[240sxOwner]

exactly....i am running rich....But my air fuel is reading soo lean that it is barely even lighting up. I want to know why my O2 sensor is reading .03 volts when it should be between .4-.6 volts. Is my ECU trying to compensate for it "reading lean" and trying to correct it with fuel

[mmatl16]

i would check your fuel pump

[wangless]

i get 15.6mpg... and im happy lol. i used to get 10 !

[PapaSmurf2k3]

DAMN that is some crappy gas mileage. Check your ECU for codes, you may have a leaky injector, or a bad coolant temp sensor or something. I just fixed my faulty coolant temp sensor, the car was running so rich it well... wouldnt run, and when it did your eyes hurt from fumes, and i was still getting better than 15mpg. Try running seafoam or carb cleaner through your system, and check to see if your O2 sensor wires or harnesses are corroded or something. Good luck

[wangless]

lets see what ive done...

seafoamed all three areasspark plugs / wirescap / rotorcoolant temp sensor o2 sensor cleaned maf / tb with brake cleaner

and probably some other stuff i remember. hey, 15 is a lot better than 10 lol

[Arrow]

wow... not to burst anyone's bubble but I get mad when I get 18 mpg... right ow I'm getting around 20 maybe a little higher...

to address your issue... I'd check to make sure your o2 sensor is good... if it's giving the ecu an incorrect signal, then that woudl cause it... but I don't know how a new o2 sensor could be bad (I know that you've got a new on on it) and I'd also check your injectors for any leaks b/c that might also contribute to it... or even check your fuel filter, that can be a very key issue and it's not very expensive to replace.

[240sxOwner]

I bought a brand new z32 filter 6 months ago...Well now for some reason...My gas mileage is going back up near 18-20, but my air fuel is still reading very lean....On the 240sx is the voltage readout on the connector gaurded/blocked? I am afraid to cut and splice the actual wire leading to the ecu. And i have the power hooked up to my shift light power wire. Should i move it? Thanks

[DAEDALUS]

Your O2 is probably clogged with soot, or it doesn't get hot enough, or both. It needs to get pretty hot to work right, kind of like a cat. The reading should jump around at least a little. If it's just sitting there it's probably not working.

[240sxOwner]

But i have tried 2 different brand new sensors....I hate Bosch by the way...lol

[wangless]

ngk ... theyre even our sponsor now !

i also changed my fuel filter, o2 sensor... no codes... no leaky injectors / gas smell.

note: not trying to thread jack

[DAEDALUS]

Maybe there's a bad harness connection. The .3v could just be the bias voltage--what the ECU feeds the sensor. The harness could be bad or maybe even the ECU. I'd do some continuity checks to verify the harness integrity, then go from there. Is the sensor heated?

Wangless, lemme know if you're ever near LAX.

[wangless]

gardena close to there ? lol

[DAEDALUS]

Actually I'm not too far from there. I go there about once a week to go shopping. 10-15 minute drive.

[wangless]

ic... im down there once in a blue moon though lol. but it would give me a reason to go down there, got some friends of friends who are there. theres even an L&L there haha. we can talk business again haha... so many changes

[deeznuttz2]

I had to much CO2 coming out of my pipe I think i'm still running hella rich...gettting like 15mpg.... I changed a lot of sensors...02, even the MAF

but the thing is @ cold starts, my car's rpm would go up and down a couple of times and the whole car would shake...I have a feeling that it's the Cat could be crack...therefore I'm running rich???

[DAEDALUS]

CO2? Or hydrocarbons? The O2 is just a measurement of things before the cat, so a bad cat won't affect A/F ratio.

If the O2 is working and the ECU knows the car is running too rich, then that means the ECU has done everything it can to lean things out, but couldn't adjust things enough. That would suggest that you have a fuel leak at one or more injectors. The ECU can control injector duty cycle, but it can't do anything about leaks. A rail leakdown test can verify this.

[deeznuttz2]

Yes, u r right, too much hrydrocrabon...My measurment is 67 and the max I can do in CA is 53... I was running rich for a while, took me a long time to fingure out the problem....so did running rich for a long time messed up my CAT?

[InsanityInc]

You're probably running rich because there's something wrong with your fuel system. OBD1 cars have very little automatic compensation for rich/lean conditions.

[DAEDALUS]

I think it's 25% correction, which should be plenty under normal circumstances. Fuel pressure is controlled by regulator/vacuum, so the only correction the ECU can make is with duty cycle (opening time). Deez--Hard to say about the cat. If you were running fine now then I'd say the cat could have been damaged previously, but you're still running rich. Fix that first, then worry about the cat later. You're close enough that if you fix the current rich condition I think you'll pass emissions, regardless of the cat condition.Things that can make you run rich:Injector stuck open (pretty rare)Injector leak past sealbad o2 sensorbad temp sensor or connectionAlso, both the O2 and the cat need to be hot to work right, so always keep the engine warmed up (don't overheat!) and slightly revved till just before the test.

[deeznuttz2]

damn Deadalus, u been a great help...this is the best fourms ever.

I think i'm getting there, cuz my engine don't smell like rotten egg anymore..

[steve s14]

first of all, i would not recommend cleaning the airflow meter unless you have no other choice. the airflow meter is a delicate sensor and can be damaged by chemicals or even water. if you suspect the car is getting poor mileage from the engine running rich, cover the basics if you do not have a check engine light on. first check the fuel pressure with the engine at operating temperature. it should be around 30psi at idle with the vacuum hose disconnected, the fuel pressure should jump to around 43psi. if that checks out ok, test the resistance in the coolant temp sensor, also check the connector at the sensor for corrosion, any kind of high resistance in the circuit will cause the car to run rich. check those things to start, cover the basics so you don't end up chasing your tail, and don't start replacing parts, unless you know they are bad, to fix the problem because the cost starts adding up and at that point, it probably would have been cheaper to pay a qualified mechanic to fix it for you.