Our Lambda ECU reads the stock narrow band O2 sensor voltage and adjusts the mixture via changes made to the frequency valve. The problem with the stock ECU is that it does not wait long enough for the last adjustment it made to take affect and makes another adjustment. Hence the mixture swings in an oscillation from rich to lean and lean to rich continually. This changing mixture is the most common cause of idle hunt. My ECU delays making another mixture adjustment until the last adjustment has resulted in the O2 sensor reading the current mixture.
When setting your dwell reading to the book value of 40 degrees (4 cylinder scale), your not adjusting the mixture but your centering the lambda system. Your mixture is fixed at 14.7 AFR using a narrow band O2 sensor. It?s really not that critical to perfectly center that dwell reading. As long as the dwell does not hit the max or min value, your mixture is 14.7 AFR. Having it close to center helps when the mixture changes due to altitude and other engine variations.
I built my REV B ECU a few years ago and have sold a few of those units. My car did idle hunt right after the lambda system went active (about 3 minuets after cold start). It would idle hunt for a few minuets after that and then would idle fine. That REV B ECU fixed (no idle hunt) that problem. My customers have also stated ?never an idle hunt?. Now a sticky idle motor or mis adjustment with the constant idle system can also cause idle hunt. The REV B ECU is a plug and play upgrade. Your dwell adjustment will not change if your stock ECU was working normally.
A lot of my customers want to keep their stock lambda or idle ECUs. This was not a problem when I could get those ECUs on Ebay for a decent price. Now it?s rare to see them offered. So I made my REV D lambda ECU which eliminates the need to return your stock unit for update. However it requires you to attach the 7 wires to my connector. Note the blue sensor wire was a shielded wire so it has two connections. I?m sure that shield is not needed. That wire runs along side the metal plate so any electrical noise will not be present at the sensor wire. I?m just going to run the single sensor wire (from the sensor to the plug in the wheel well, it?s just one normal wire). I did provide a pin for that shield wire anyway. Also my REV D has an extra pin that can drive a remote LED.
If you have any questions about our lambda system, ask me now that I?ve got it all fresh in my mind just completing that new ECU.
