AFR difference - bank to bank
Thread Starter
Teching In
Joined: May 2011
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AFR difference - bank to bank Here's a fun one and I'm looking for some additional feedback in hopes someone with more experience than I can help me solve this issue.
The car seems to run and drive fine but I noticed one bank running leaner than the other recently. I've had the car running in this same configuration for months. It doesn't run rough or have any issues at idle. Both banks usually run pretty close in AFR but seem to be a bit off lately.
6.0 with holley dominator efi, twin turbo.
Issue: Left bank 14.7, right bank 12.2 AFR (at idle) with learning enabled on the left bank.
What I've tested:
Swapped sides for coils, coil harnesses, injectors and WB O2 sensors. The same bank stays lean.
Tested for fire at all coils, and tested injector harness with NOID light on all injectors.
No exhaust leaks on either side.
No issues with either turbo, and no oiling.
Compression checked all cylinders and leak down test without issues.
Plugs read similar on both sides.
Checked all wiring and grounds, no issues with voltage found at neither coils nor injectors.
At this point I'm just about out of ideas and just curious if anyone else has run across this scenario.
The car seems to run and drive fine but I noticed one bank running leaner than the other recently. I've had the car running in this same configuration for months. It doesn't run rough or have any issues at idle. Both banks usually run pretty close in AFR but seem to be a bit off lately.
6.0 with holley dominator efi, twin turbo.
Issue: Left bank 14.7, right bank 12.2 AFR (at idle) with learning enabled on the left bank.
What I've tested:
Swapped sides for coils, coil harnesses, injectors and WB O2 sensors. The same bank stays lean.
Tested for fire at all coils, and tested injector harness with NOID light on all injectors.
No exhaust leaks on either side.
No issues with either turbo, and no oiling.
Compression checked all cylinders and leak down test without issues.
Plugs read similar on both sides.
Checked all wiring and grounds, no issues with voltage found at neither coils nor injectors.
At this point I'm just about out of ideas and just curious if anyone else has run across this scenario.
You say learning is enabled on the left bank, and left bank
is giving the right answer. What's the deal on the right
bank? Omission indicates not-enabled (maybe a sensor
code, inhibiting trimming there?).
is giving the right answer. What's the deal on the right
bank? Omission indicates not-enabled (maybe a sensor
code, inhibiting trimming there?).
Thread Starter
Teching In
Joined: May 2011
Posts: 40
Likes: 1
There is a difference of a 1-2 full points in AFR when cruising between both banks. It appears that under WOT they both level out. Not sure where to look for the AFR being off so far at cruising speeds and which sensor to actually use for the autotune.
You have an exhaust leak somewhere...
Even a pinhole can cause it to read lean on one side...
Have an exhaust shop smoke the exhaust and you will find the leak...
Then you can have them just seal it up while they are at it.
Either that or you have a bad injector on one side..
How is closed loop set up?
Does it read left o2? Right o2 Richest o2? Leanest o2? Or average of both o2's?
Even a pinhole can cause it to read lean on one side...
Have an exhaust shop smoke the exhaust and you will find the leak...
Then you can have them just seal it up while they are at it.
Either that or you have a bad injector on one side..
How is closed loop set up?
Does it read left o2? Right o2 Richest o2? Leanest o2? Or average of both o2's?
Are you seeing any misfires difference bank to bank?
One cylinder misfiring, even a little, can mess with the
wideband a lot (and, going to WOT at more enrichment
and less advance, might make that go away). This might
be an injector imbalance kind of deal, a single runner
vacuum leak, etc.
One cylinder misfiring, even a little, can mess with the
wideband a lot (and, going to WOT at more enrichment
and less advance, might make that go away). This might
be an injector imbalance kind of deal, a single runner
vacuum leak, etc.
Thread Starter
Teching In
Joined: May 2011
Posts: 40
Likes: 1
I resealed the exhaust and made sure it wasn't leaking. Injectors aren't the issue as I've swapped banks on them. It's and edelbrock efi intake, no vacuum leaks on the runners. I'll be pulling the drivetrain loose to see if there are any issues with a flat lobe because it has been a very strange issue.
Thread Starter
Teching In
Joined: May 2011
Posts: 40
Likes: 1
Pulled the intake and there's a build up of what looks like tar on the #3 cylinder intake floor and the valve appears to be 'wet' which I'm assuming is oil on the back side. It's in a strange place considering it's right under the injector and doesn't appear to be the usual valve guide leakage. I found this same tar like build up on the injector tip when I pulled it. I cleaned the injector and swapped sides previously. I've never seen one build up tar like this on so few miles (less than 1k miles on this setup and all new hardware on the head)
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Teching In
Joined: May 2011
Posts: 40
Likes: 1
You have an exhaust leak somewhere...
Even a pinhole can cause it to read lean on one side...
Have an exhaust shop smoke the exhaust and you will find the leak...
Then you can have them just seal it up while they are at it.
Either that or you have a bad injector on one side..
How is closed loop set up?
Does it read left o2? Right o2 Richest o2? Leanest o2? Or average of both o2's?
Even a pinhole can cause it to read lean on one side...
Have an exhaust shop smoke the exhaust and you will find the leak...
Then you can have them just seal it up while they are at it.
Either that or you have a bad injector on one side..
How is closed loop set up?
Does it read left o2? Right o2 Richest o2? Leanest o2? Or average of both o2's?
Thread Starter
Teching In
Joined: May 2011
Posts: 40
Likes: 1