[dlginnc]

Did you perform the Idle Learn Procedure after replacing the O2 sensor? When you disconnected the O2 sensor lead the PCM goes into a pre-programmed 'limp' mode designed to get you off of a busy highway. The PCM needs a good baseline to operate correctly and the starting point is the idle learn procedure.



Idle Learn Procedure: When Idle Learn Procedure: When and How to Do It

All Honda models with programmed fuel injection
(PGM-FI) have the ability to learn and adjust the
engine idle speed to optimize engine idle
characteristics.

The idle learn procedure should be done
whenever you do any of these actions:

• Reset, replace, unplug, or reprogram the ECM/
PCM

• Disconnect or replace the battery

• Do engine work that requires R&R of the
intake manifold or the throttle body
To allow the ECM/PCM adaptive idle speed
system to learn and adjust the engine idle speed,
here’s what you do:

• Make sure all electrical items (A/C, audio unit,
defogger, lights, etc.) are turned off, then start
the engine.

• Let the engine reach its normal operating
temperature (the cooling fans cycle twice; the
coolant temperature is about 194° F).

• Let the engine idle for at least 5 minutes with
the throttle fully closed and with all electrical
items turned off.

• If the cooling fans cycle on while doing an
adaptive idle learn, add the time the cooling
fans are on to the 5 minute adaptive idle learn
time.


Found at:


Idle Learn / PCM reset thread

 

[dlginnc]

chiody
You are correct. The idle learn procedure is not neccesary. It simply reduces the amount of time to complete all PCM readiness cycles and insures that the PCM can control the engine for driver safety when initailly driving after the reset.

To execute the idle learn procedure you need to reset the PCM. That alone will probably either fix the issue for Nomadman or tell him that a 'OEM' O2 sensor replacement might be the next step.
After all we are guessing what the real root cause is here.