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Intermittent Lean in Closed Loop

 
Old 05-31-2019, 08:15 PM
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Default Intermittent Lean in Closed Loop

Before I start please forgive that this is an 06 Silverado 5.3 lm7 not a Camaro etc. Can't find any decent active forums other than here!

Having an intermittent lean 16:5+ only in closed loop after 3rd gear shift and will come back to stoich when coming to a stop and idling. Open loop is perfect. Just started happening the past couple weeks of a solid year after being dyno tuned. (Tuner did not tune in lean cruise) I can physically feel and hear when it goes lean then occasionally it will just snap out of it like an on/off switch. So I know it's not the wideband out of calibration.

Mods:
Btr stage 4 cam
Circle d 3200 converter
Long tubes/y pipe
Only have upstream o2's (replaced thinking that was the cause)

Any help pointing in the right direction would be much appreciated!
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Old 05-31-2019, 08:36 PM
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I'd be curious what your fuel pressure is during these periods of lean operation. I know you said open loop was perfect but I'm still curious.

Rick
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Old 05-31-2019, 08:36 PM
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Checked for dirty MAF? If you use one...
BTW don't apologize for it being a truck. There are as many trucks on this forum as all other kinds of LS-powered vehicles.
Welcome to the forum!
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Old 05-31-2019, 08:50 PM
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Originally Posted by B52bombardier1 View Post
I'd be curious what your fuel pressure is during these periods of lean operation. I know you said open loop was perfect but I'm still curious.

Rick
That has crossed my mind. It's 60psi at idle, but that's not when it's acting up. Just might have to get a cheap electric gauge to see while driving.

Originally Posted by G Atsma View Post
Checked for dirty MAF? If you use one...
BTW don't apologize for it being a truck. There are as many trucks on this forum as all other kinds of LS-powered vehicles.
Welcome to the forum!
Thanks!
Have cleaned the MAF (with proper cleaner) also checked for exhaust and vacuum leaks.
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Old 06-01-2019, 12:24 AM
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If you can, data log and see what your ECT is when it goes lean. Iím dealing with that right now with my turbo 5.3 swapped 67 Chevelle.. it was stuck in open loop, finally tracked down why it wouldnít go into CL. Once I figured it out I began to drive it and all of the sudden it started running super lean (my wideband was reading 19.05) just cruising around. Had to limp it home.. went back and looked at the data log and every time it began running rough (lean) the temp would go from 195 down to 20 or -35.... so Iím guessing my autozone ETC sensor **** the bed. Just something to consider..







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