Air Fuel at Cruising, Light Load

[DRock9]

I recently had my car tuned by Dez and installed an air fuel gauge which made me notice I run really lean during idle and cruising with light load, at around 16-18+ on my gauge.

This is with one of the O2's unplugged, I always read it goes really rich if one or both are unplugged so what gives?

Anyways, I made this thread to ask how the ECU decides how much fuel to dump into the cylinders at cruising/light load so that I can go around and check what might be causing my car to run so lean. I am aiming atleast to get it down to around 13-14.

Thank you.

 

[Foxfan88]

normally with everything working the EEC will go into Closed loop and rely on o2 feedback to trim fuel to stoichiometric (14.7:1 AFR)

in closed loop the EEC will be constantly adding and taking away fuel. if the EEC is seeing rich from the o2s, it will take away fuel until it starts getting lean readings. at this point it will start dumping in more fuel until it gets more rich readings. and keep doing this. and keep boucning around stoichiometric. the o2s have a switch voltage around .45V, any voltage below that means lean to the EEC, anything higher means rich.

ive noticed in CL the AFR will never settle on 14.7 it will bounce around. from say like 14.4-15.1 will usually swing in that area.

if your starting the car with one o2 unplugged the EEC shouldnt let the car into CL(not 100% sure on this someone else will need to confirm), so it will run in OL. and if the MAF curve isnt perfect. the AFRs could be a bit off.

perhaps your WB needs a fresh air recalibration, may not be reading accurate.

 

[DRock9]

Hmm...it's a brand new wideband from Kurgan, I hope it doesn't already need a calibration.

Thanks for clarifying how the EEC determines how much fuel to give the engine, I am going to make an appointment ASAP to get another bung welded on so that I can put my O2 back in to see if that improoves anything.

 

[ninety15.0]

Do you have a check engine light. If the O2 is unplugged you would most definitely have a CE light?!

My only guess is that the tuner might have the computer in forced open loop? This is somewhat common on blown applications if the tuner is being lazy! What happens under moderate part throttle? WOT?

 

[DRock9]

It runs the same until I hit WOT, when I hit WOT it runs fine.

For a couple minutes after I hit WOT it will run really good, like in the 11's-12's at idle and light load but then it goes back to 16-18.