[Diy_efi] Post 4-Wire O2 Sensor Swap Observations...

[gary]

RE: [Diy_efi] Post 4-Wire O2 Sensor Swap Observations...> Popping on decel is from lean, not rich... 

DFCO code in PCM cuts fuel when throttle blades are closed rapidly 
from a point of sufficient rpm.  By design, the PCM cuts all fuel to the 
engine, with resulting cleaner emissions and NO popping. 

The O2 sensor monitors the amount of oxygen in the exhaust, hence 
the name O2 sensor.  Typical of an O2 sensor reading lean include 
an exhaust leak and ignition issues causing plugs to not fire.

The exhaust leak allows outside clean air (and oxygen) to be 
sucked into exhaust.  The O2 sensor reads this additional clean air
as a lean condition, relaying this info to PCM, which then adds fuel
to combustion process.  This ends up causing a too rich AFR.

The O2 sensor will view unused/unburned oxygen, due to a plug not
firing as a lean condition.  The O2 sensor is not capable of sensing
fuel.  All plug wires on one side could be pulled, to imitate plugs not
firing, causing raw gas to drip out of exhaust.  The O2 sensor would 
read this as a LEAN condition, due to the extra unburned oxygen. 
This extra oxygen that was allocated for the fuel that was not burned. 

GAS

----- Original Message ----- 
  From: Donovan, Larry 
  To: 'diy_efi at diy-efi.org' 
  Sent: Friday, April 22, 2005 12:19 PM
  Subject: RE: [Diy_efi] Post 4-Wire O2 Sensor Swap Observations... 
  -----Original Message----- 
  From: David Cooley [mailto:n5xmt at bellsouth.net] 
  Sent: Friday, April 22, 2005 12:35 PM 
  To: 'Mike Frels'; diy_efi at diy-efi.org 
  Subject: RE: [Diy_efi] Post 4-Wire O2 Sensor Swap Observations... 

  Popping on decel is from lean, not rich... 
  And if you had an exhaust leak before the O2, it may read lean, but mileage would go down the toilet as it would be richening the mixture up to compensate.



  Neither of these make sense to me. How can popping be from lean and how can an exhaust leak cause the oxygen sensor to read lean? How can an exhaust leak changehe amount of oxygen remaining in the exhaust. Please explain.
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