SR20DET Erratic ignition angle when idle speed control (ISC) turned on

[Jeffrey]

I'm getting some weirdness going on when I have the ISC enabled and it's engaged. The ISC valve is working as far as I know. I can use the Aux test and I hear it click open. But when I have it enabled, the ignition angle goes crazy, like it's trying to lock in but doesn't. I have included the log file where my car is not driving, just turned on and idling. I had it turned on and at around the 40 second mark I turned it off, you can see the ignition angle stabilize. Is this normal?

PC Datalog - 2024-05-23 7;56;09 pmIDLE-ON-OFF.llgx SR20DET - DATSUN 510.pclx

[essb00]

It is not crazy. That's idle ignition control doing exactly what it is supposed to do -- catch idle speed overshoot/undershoot quicker than the idle actuator can do.
You still need to have the proportional and derivative gains tuned, the idle actuator control integral gain, idle base position table, and other offsets so it will be able to maintain idle speed target with very less fluctuations.

[Jeffrey]

I guess the issue I am having is that I am running extremely rich at cold start, which I thought was due to the idle. If I turn off the Accel Enrichment, it goes over to full lean. But when I try changing the parameters in the Accel Enrichment tables, it has no effect, only when I turn it off. If you take a look at the Lambda AFR during the 1st 7 minutes of the log, those wild swings between full lean and full rich are me turning on and off the Accel Enrichment. The AFR starts hitting the AFR target around the 18:40 mark, when the ECT reaches 205 ºF. I'm trying to see what I can do to get a more stoich AFR during initial start up.

 

Link for a copy to my log: https://drive.google.com/file/d/1tlCHlcvFAlLlI66-KjR91dXjLnzNfQNe/view?usp=drive_link

[Adamw]

Your accel deadband needs to be set above your normal TPS delta noise level.  Having said that, your TPS signal is very noisy, I think you need to investigate and improve that rather than just increase the deadband.  Your TPS delta is about +/-8% with the throttle closed and closer to +/-20% at steady state cruise, it would more typically be less than 1% under both of these conditions.  I dont think you will ever be able to get good accel fuel or close loop lambda etc with it this bad. Check the sensor doesnt have backlash on the throttle shaft, or it is a sprung sensor to take up the backlash, if that looks ok then the sensor is faulty or there is a wiring problem.  

[Jeffrey]

You came through for me again. 👍

 

The TPS sensor is fairly new, about 2 years old from the dealer. But when you said to check my wiring, sure enough, my sensor grounds (ECT and TPS) were tied to my chassis/engine ground. Luckily it wasn't a hassle to find the point where they connected on my harness and separate them so the sensor ground and engine ground are not connected when the engine is running. I also readjusted the physical TPS sensor on the throttle body did another TPS calibration on the ECU to be sure everything was on point. I included a screenshot of the TPS calibration voltages and the log when I started the car. TPS voltage and delta are stable now. Granted it's at idle, I didn't drive the car, but the difference is night and day.

 

Log in this link: https://drive.google.com/file/d/1r2_bg1eP35LqXmnyoswqbLXDbUJ4yIGV/view?usp=drive_link