Quote:
Originally Posted by massmike
Another update... I was able to add a 3 wire O2 sensor to the car. I used a Bosch 13918 which was powered with a relay. I used a positive signal from the unused thermo valve plug that I mentioned above and constant 12V came from the Heater fan fuse in the rear fuse panel. Unfortunately this made little to no difference in the surging effect while driving with light loads.
I also spoke with the folks at Systems Consulting regarding the ECU box. They mentioned that these Lambda boxes are generally pretty reliable and generally work or don't. I described the problem I was experiencing and they didn't feel that the ECU would be to blame but did offer to test it for me.
https://systemsc.com/index.htm
I am still on the hunt for the next thing to check |
IF the ECU is not at fault, then the cause of the surging is actually quite simple: regardless of the lambda control in your case the CIS system obviously does not provide a stable mixture or AFR under steady-load driving conditions. The AFR swing (its amplitude) is so large that the original ECU cannot compensate quickly or effectively enough, causing the mixture to become intermittently too lean — which results in surging. You can deactivate the regulation and drive as suggested earlier in this thread. However, that means you must enrich the base mixture in static open-loop mode so that the highest AFR peak does not exceed 14.7:1.
But as mentioned, this does not eliminate the root cause — the engine will still run incorrectly, since this would also mean that under certain operating conditions, the mixture becomes too rich. It may result in smooth driving (as you already reported), but with improper fueling and the associated drawbacks.