running lean and rich!!

[TeamRedLine23]

so I lost my drivers license about 9 months ago becaise I had a siezure and lost control of my 300zx. So I went out and bought a project car. i figured by the time i get my license back the car will be done.

anyways i cant really tune the car because I cant really test the car after I make an adjustment to the maf trans and the s-afc2. I got the car to idle perfect, but at idle (about 850-870 rpm) the car runs really lean. on my aem air/fuel gauge it reads about 14.5...when I rev the car it runs about the same but when i let go of the gas pedle it runs 19 then goes back to 14.5...so I made some adjustments to the maf trans and now the car runs 10.5 when under load (making boost) then goes back to 14.5 at idle.

the question. is it normal for the car to run lean at idle?

[Talon69]

not sure about lean but my car runs a little rich at idle with all my mods.

Maybe the best thing to do is have someone take it down the road with you in it to get a better tune?

[TeamRedLine23]

thats why i want to get it dyno tuned by a pro. I do take it up and down te street, no matter what adjustments i do to the maf trans it still the same.

[defiancy]

Maybe you need to make some minor adjustments to your timing.

[crunchymilk55]

first off don't trust the readings unless it's a wideband

at idle, our cars should go back and forth, 14.5 being the middle. This is called the ecu's "closed loop" mode. Look that up if you want more info. Whenever we talk about running 11:1 or similar, we are talking WOT or close. After a certain amount of throttle, the ecu will kick into open loop mode, and that's when we tune. We really don't care about closed loop, that's only when the car is idling or driving around town. Basic fuel compensation will automatically deal with this. The car is cycling back and forth getting readings from the 02 sensor to get the best fuel mileage. In open mode, the 02 sensor doesn't even really read anything, the ecu is calculating what the a/f ratio SHOULD be, it has no way of knowing what it actually is. That is why narrowband 02 gauges are useless.

Let me know if you need any more clarification.

[TeamRedLine23]

that was a perfect. I understand now. that cleared up a lot of things. thanks. and yes, I do have a wideband.

[crunchymilk55]