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DieselJeepSJ
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O2 voltage low, lean code, high idle
Sep 19th, 2019 at 3:59pm
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Hi, I have a few things happening right now on the dually. I have an intermittent issue with a high idle, and it came back yesterday and would not go away once the truck was hot.

I did some basic data logging and found this -
1) IAC counts are in the 30's at idle.  When I installed this TB, I set the minimum idle speed and when things are behaving the IAC counts are in the mid-teens.  Something is commanding higher counts and I have no idea what.

2) O2 sensor voltage is all over the place.  While driving and trying to hold steady cruise, I see voltage from 0.999 all the way down to 0.015v.  O2 is a heated 3-wire.  Could sensor be toast?

Per data logger, temp was consistent in the 188-192 range for the entire test.  MAP was low 30's at idle and saw as high as 70's while driving so I think MAP is OK.

I did just notice from the logs that while I'm driving the system is going in and out of closed loop during steady cruise.

Idle was sitting right at 1000rpm, and O2 voltage at idle is constant >0.910.

What has been done to truck to get it to run right-
2 brand new fuel pumps (the later model, higher volume units) and new fuel filter.  TBI was rebuilt with bushed/O-ring shafts and new injectors.  New IAC and TPS.  All vac lines replaced.  O2 converted to heated 3-wire.

Thoughts?  Suggestions?
  
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DieselJeepSJ
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Re: O2 voltage low, lean code, high idle
Reply #1 - Sep 19th, 2019 at 8:32pm
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Also, my manifolds are getting so hot that the plastic loom on wiring about 6" away is melting.
  
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