I need to know what my air fuel gauge should be reading. lean at idle and rich when i give it gas?

 

The car (once warmed up) is in closed loop during idle which should not be either rich or lean.

Light acceleration should still be in closed loop (neither rich or lean).

WOT or strong acceleration will got to open loop and be rich as the computer doesn't have enough info to keep it in closed loop, so it enriches the mix just be safe.

When accelerating and then suddenly lifting off the throttle, you'll temporarily go open loop. I believe it goes lean at this point as the computer cuts the fuel.

Someone correct me if I'm wrong.

 

Yeah, it dumps fuel in under acceleration to be on the safe side and prevent detonation and under deceleration, it leans out the mixture for better emissions. The only time the ECU is in open loop is under full throttle.

 

Actually, that's no always true. According to my OBD2 device, my car goes open loop under these conditions:

- when car isn't warmed up and water temp is < 110 deg

- when accelerating and you suddenly release the gas pedal (to lean out the mix to conserve fuel, as you said)

- when accerlerating at WOT and "near" WOT. In many cases, I'm just at 75% throttle and it goes open loop. (Maybe it's cuz I'm hitting the resonance range of my CAI?)

 

I agree with the 1st and 3rd ones you stated but I am not too sure about the other one. I guess I will have to do some research and get back to you. :thinking:

 

all good info thanks it does all the above. But when I'm at idle and warmed up it should it stay at rich at idle cause mine bounces from rich to stoich (problably not righ spelling) it does not just stay on rich (left hand side of guage) should it bouce around like that or what?

 

It should bounce.

After warm up, during idle, it should be in CLOSED LOOP, which means bouncing on a regular A/F guage. You don't want it rich then, cuz you are wasting gas.

 

1 & 3 are considered open loop (all though your CAI has nothing to do with it, it's a value in the ECU that coresponds to a MAP sensor value that determines it.)
but 2 is not really worded right. If you're accelerating hard and let off the throttle a little to cruise the ECU will be in closed loop. If you're accelerating hard or cruising and let off the throttle completely then ECU shuts off the injectors. Not really closed or open loop...

 

i assume you have an autometer a/f gauge? all it does is bounce around. get a wideband o2 if you want something thats actually useful.

 

Correct. You should go full lean when completely off-throttle.

While everyone's on the correction kick today , I thought I'd point out that an a/f gauge doesn't give you info about your a/f ratio. It just tells you how well your o2 sensor is working because it just reads 0-1 volt based on what your o2 sensor smells. It's not accurate.

Your air/fuel ratio is a calculation that determines how much air is in your fuel. Ideally it's supposed to be 14:1, but many engines prefer a different ratio. I run 12:1 for safety reasons and still get knock at 21 PSI. If I could get 100+ octane gas, I'd run a leaner ratio like 14:1 and get much better gas mileage.