the reasons to cause the car running lean??

[nicku]

as the subject, what are the reasons to make the car run lean??

[NINJASPY]

gas and air. honestly your question cant be any more vague.

[nicku]

i know...i mean what's the reason to cause the car running lean. because my car was running rich before, and couple days ago, i tried to tight up the bov screw, after that now the idle is like low 15 on my wideband. and I did search online, the tightness on the bov screw doesnt not make the car run lean. Only if it is TOO loose, then the car might run rich. So I thought my car was running rich because of the screw was too loose. and actually my car is running lean. My car has stock boost 7psi, stock injectors 370cc and stock maf. Its a SR redtop. right now, I tried to adjust by the safc so the car doesnt run lean anymore. But im just wondering why everything is stock but the car is lean??

[louisdaboois]

you can check the bolts and gasket to the turbo elbow... also if the downpipe is properly secured. cause a little exhaust leak in those 2 joints can effect the reading of the o2 sensor by alot.

[EAT Motorsports]

exhaust leaks can cause lean reading because of air entering the exhaust stream... anyways...are you lean under acceleration is the real question... 15 at idle is fine/ normal.... do you want to use all your gas idling?

[nicku]

well...when the car is courising like when I just hold the throttle maintain like 40 miles per hour, the car is like low 15's as well...other than that, when I floor the gas, the car is going like 13s or so. is it normal? how is the car supposed to be actually? I mean during idle, cruising, or flooring the gas. or even just step on the gas a little harder than cruising but not flooring it.

[nicku]

my another question is.....lets say my exhaust is not leaking. is there any other reason that cause a stock setup running lean?

[EAT Motorsports]

vac leak, low fuel flow ( dirty injectors, Fuel Filter), also just asking if you have your narrow band hooked up or what are you doing for that? Also crusing/ idle should be high 14s, wot should be low 13ish.. on a stock ecu, so i think you are doing fine just check over your car for the above....

[nicku]

i dont have narrow band, i have the plx m300 wideband. well..i have changed to the walbro 255. and im going to pick up 555cc nismo injectors on this weekend. so hopefully, i have time to check over everythign before i install them.

[EAT Motorsports]

okay so you have the narrow band output hooked up to your ecu right? good luck also sent you a PM on the injectors.

[nicku]

yeah the narrow band which is the stock o2 sensor is hooked up to the ecu and the wideband is on the downpipe close to the cat. i believe thats the correct way, right?

[EAT Motorsports]

yeah, seems like everything is fine, just double check everything. if its above 13s on stock tune at WOT then you should be worried...

[nicku]

well...if at wot, the number keeps changing between 13-14....is it okay? by at wot, it means flooring the throttle all the way right? but does it mean all the way to the redline or what? sometimes my wideband reading doesnt read the same. for example, sometimes when im cruising, the reading is like 12 or something. but sometimes is at low 15. and sometimes when i floor the gas a little bit like until 5000 rpm, the number just constantly keeps changing.

[nicku]

anybody helps???

[Omarius Maximus]

The most common reason for running lean is a vacuum leak. When your just cruising around, the afrs are supposed to be fluctuating because your ecu is in closed loop and constantly adjusting the fuel with the help of your 1st 02 sensor. It's when you floor it that it should stabilize. You want to be at 12.5 or less. Maybe you have a slight vacuum leak, pressure test your system.

[nicku]

oh by the way, i have a s15 t28. but everything else is stock