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Hi Art,
Yes - just like you'd indicated in the IAC thread, Pin 12 on the ECU is also connected to 15 on the ICU. That's the reason for those 2 pin-12s.
I've given up trying to disable the IAC via the grounding of pin 12 - just dont get any rpm change. The engine is idling nicely now at around 750. Idle-Bypass screw is fully closed to compensate for very-slightly open butterfly-valve. Never had the car start and idle as well as it currently does: on cold, it surges to 1200 rpm on start, and slowly (5 secs or so) settles to 750. Certainly worth all that extra effort. Couldn't have done it without you'll - so thanks a lot !
Over the weekend I turned my attention to setting the CO level. I have a spare AMM that had the adjustment-screw plug removed, so I swapped that with my current AMM. Both the AMMs had their pot.resistance set to around 380 ohms (didn't check the voltage as you reccomended since I didn't know what pins to check on the ECU at the time). Before I started adjusting the pot - I checked and found that 15 full 360-degree adjustment turns is all it takes to go the full range of the pot. When I rigged up the test LED-circuit between ECU pins 22 and +12v, I found it was lit up all the time. After adjusting the pot almost all the way to one end, it started blinking nice and steady. I then rigged up the LED so I could drive and watch how the rich/lean settings changed while driving. Experiment was so interesting I plan on rigging the LED up permanently using a spare dash bulb-socket.
After I finished my adjustment, I checked the resistance & voltage. Resistance between AMM Pin 6 and ground (or Pins 1,3 or 4) is around 100 ohms. Voltage between Pin 6 and ground is a mere 0.55 volts. Is this resistance/voltage setting way off ? As I said - test LED blinks nice and steady (about 50% duty-cycle as best I can tell). To make sure there was no wire-resistance coming into play, I verified these values at the ECU pin 14 as well. I suspected my Bosch O2 sensor might be off (it's 8 years old now) - but I tested it and it generates a healthy 0.2 -> 0.9 v - so no reason to change it.
So I guess my tune-up is done (though I still need to replace my 8-year fuel-filter & original filter-sock). Am curious to see what my next CA emission test report is: I keep all back reports for comparison, but this will be the first one on a dyno. They've never raced the engine on park in previous tests because the ZF22 warning immediately pops-up on all their test-rigs.
I've made so many tuning-changes now I'm curious to see how much (if any) it affects mileage.
Thanks for all your help !
Noel
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