Bung installed – $40 at an exhaust shop.

Here is the O2 sensor installed

Connected to the 14point7 Spartan 3

The Spartan 3 is powered from the same place as the Pertronix module – the 12V side of the blue ballast resistor. This is only powered when the engine is on, which is a requirement for the Bosch 4.9 LSU O2 sensor.

And finally the CAN bus output from the Spartan 3 was connected to my laptop.

My laptop was running professional CAN bus monitoring software that I already had which allows me to visualize and log the AFR reading. The Spartan 3 gives a Lambda output multiplied by 1000 so I needed to take that value and multiply it by 0.0147 to get the AFR.

At cold start the AFR was 10.5 and as the engine warmed up and the AAV closed the AFR increased to about 11.5. Note that my MPS at this point was not tuned (I had turned it enough to stop the engine from significant shaking, that is all).

I noticed that if I put the car into drive the AFR jumped up. Strangely when the engine was warmed up the AFR started dropping again – I am not sure why.

I then disconnected the air temperature sensor so I could lift the air box up and disconnect the throttle position switch, then I reconnected it. Disconnecting the air temp sensor caused the AFR to significantly drop.

Next I adjusted the MPS to get an AFR of 14.3.

This was followed by disconnecting the air temp sensor again so I could lift up the air box and reconnect the TPS.

Finally I turned the ECU rheostat four clicks clockwise to set the idle AFR at 12.8.

These numbers come from Graham here.

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