Well the deed is done.
Some of the threads about supercharger idle (with contribuitons from Slydit - thanks !) started me thinking about whether my O2 sensor was working. Turns out it was located miles downstream of where it should have been (thanks to aftermarket headers) - in fact it was only about 400mm in front of the cat converter by the time the 4-2-1 had done it's stuff. So the poor thing was 1) certainly old & 2) probably cold.
After much deliberation I got a 4 wire Denso sensor off a very late 1.6 NB at Ace of Parts near the Auckland saleyards (the engine only had 2,000 km on it !). I took note of the wire colours on the loom side of the plug that connected the sensor to the loom - that way I thought I could track which sensor wire did what.
Not so easy - tried to use the madracki wiring diagrams but they were only for 1.8 engines & didn't quite match. Ended up ringing the technicians at John Andrew who looked at their diagrams - again they only had 1.8 diagrams but at least their colours matched mine !
Installed the sensor Saturday afternoon - took a couple of hours including farting around getting the car up etc etc.
And the result - great! Running the engine in the garage I seemed to be getting the right range of voltages coming into the PCM. The sensor also got hot if I left the ignition on for a couple of minutes. On the road the car is measurably faster & idles perfectly. Unfortunately I didn't do a performance test with the new O2 only - but the combined effect of a lightened flywheel & the new O2 sensor is a 3.7% improvement in 2,000 to 6,000rpm times in second gear. (OK, OK - I know it's not that scientific but faster is faster no matter how you get it!
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So - there you go. I'll be interested to see the longer term impact on driveability, fuel consumption, colour of exhaust pipe (quite sooty now) & the dreaded droopy idle !
With thanks to Slydit (for techy stuff) & David M (for moral support)
Regards,
(idle droop that is ....)
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Gazda in the white HOT Mazda 