Lean AFR at Idle
#1
Newbie
Thread Starter
Lean AFR at Idle
Hi,
I recently installed wideband sensor on my car(installed near the rear O2 sensor), and noticed lean AFR during idle, around 17-17.5. Front O2 sensor fluctuates between 0.5-0.7V when WDB is reading 17-17.5. I get more or less better AFR reading when cruising around 15-15.5. Any ideas why it is so lean at idle?
My setup:
Gsc S1 Cams,
Blitz Air filter.
Checked for boost leaks. No issues there.
Also didn't see any exhaust leaks, when visually inspected.
P.S. Don't know if it's realted or issue at all, but noticed that when pressing brakes during idle, AFR goes around 19-20.
I recently installed wideband sensor on my car(installed near the rear O2 sensor), and noticed lean AFR during idle, around 17-17.5. Front O2 sensor fluctuates between 0.5-0.7V when WDB is reading 17-17.5. I get more or less better AFR reading when cruising around 15-15.5. Any ideas why it is so lean at idle?
My setup:
Gsc S1 Cams,
Blitz Air filter.
Checked for boost leaks. No issues there.
Also didn't see any exhaust leaks, when visually inspected.
P.S. Don't know if it's realted or issue at all, but noticed that when pressing brakes during idle, AFR goes around 19-20.
#4
Evolved Member
Hi,
I recently installed wideband sensor on my car(installed near the rear O2 sensor), and noticed lean AFR during idle, around 17-17.5. Front O2 sensor fluctuates between 0.5-0.7V when WDB is reading 17-17.5. I get more or less better AFR reading when cruising around 15-15.5. Any ideas why it is so lean at idle?
My setup:
Gsc S1 Cams,
Blitz Air filter.
Checked for boost leaks. No issues there.
Also didn't see any exhaust leaks, when visually inspected.
P.S. Don't know if it's realted or issue at all, but noticed that when pressing brakes during idle, AFR goes around 19-20.
I recently installed wideband sensor on my car(installed near the rear O2 sensor), and noticed lean AFR during idle, around 17-17.5. Front O2 sensor fluctuates between 0.5-0.7V when WDB is reading 17-17.5. I get more or less better AFR reading when cruising around 15-15.5. Any ideas why it is so lean at idle?
My setup:
Gsc S1 Cams,
Blitz Air filter.
Checked for boost leaks. No issues there.
Also didn't see any exhaust leaks, when visually inspected.
P.S. Don't know if it's realted or issue at all, but noticed that when pressing brakes during idle, AFR goes around 19-20.
#6
Evolved Member
#7
Newbie
Thread Starter
Thanks for replies guys!
I got tuned after I changed those things, I though it was exhaust leak issue since my manifold had little crack but I changed manifold, and it still remained. Tuner says this lean conditiin is caused by cams, meaning big overlap, and says he can't get it more rich.
What was the system voltage when you had that issue? I don't rally have any other issue(well turbo needs rebuild), idle is stable and runs/pulls more or less fine.
What causes confusion for me is that, O2 thinks afr is fine, as I understand 0.5-0.7volts doesn't mean it's lean. Also what that braking making it more lean, is it normal behaivor?
I got tuned after I changed those things, I though it was exhaust leak issue since my manifold had little crack but I changed manifold, and it still remained. Tuner says this lean conditiin is caused by cams, meaning big overlap, and says he can't get it more rich.
What causes confusion for me is that, O2 thinks afr is fine, as I understand 0.5-0.7volts doesn't mean it's lean. Also what that braking making it more lean, is it normal behaivor?
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#8
Evolved Member
Thanks for replies guys!
I got tuned after I changed those things, I though it was exhaust leak issue since my manifold had little crack but I changed manifold, and it still remained. Tuner says this lean conditiin is caused by cams, meaning big overlap, and says he can't get it more rich.
What was the system voltage when you had that issue? I don't rally have any other issue(well turbo needs rebuild), idle is stable and runs/pulls more or less fine.
What causes confusion for me is that, O2 thinks afr is fine, as I understand 0.5-0.7volts doesn't mean it's lean. Also what that braking making it more lean, is it normal behaivor?
I got tuned after I changed those things, I though it was exhaust leak issue since my manifold had little crack but I changed manifold, and it still remained. Tuner says this lean conditiin is caused by cams, meaning big overlap, and says he can't get it more rich.
What was the system voltage when you had that issue? I don't rally have any other issue(well turbo needs rebuild), idle is stable and runs/pulls more or less fine.
What causes confusion for me is that, O2 thinks afr is fine, as I understand 0.5-0.7volts doesn't mean it's lean. Also what that braking making it more lean, is it normal behaivor?
if you can try replacing the altenator aswell.
#9
Account Disabled
#10
Newbie
Thread Starter
#13
Evolved Member
I would check the fueling with the OE O2 sensor closed loop correction turned off.. thast way you have good base fueling and can then see if the O2 sensor is giving you trouble..
which WB are you using?
#14
Evolved Member
If your afr goes leaner with the brake pedal depressed it can be a vaccum leak at the brake booster.
Go under dash and press brake pedal listen for a hiss noise from booster. Maybe spray brake cleaner at the back of the booster inside the car while pressing the pedal. See if engine stumbles
Go under dash and press brake pedal listen for a hiss noise from booster. Maybe spray brake cleaner at the back of the booster inside the car while pressing the pedal. See if engine stumbles
#15
Evolved Member
yeah, maybe he could block the vacuum line just to se if it behaves normally