square wave pattern in datalog

[pit_celica]

I think that you are splitting hairs here. In the above datalog, the MAP if following the TPS signal nicely. The TPS is nice and flat. The MAP signal is quite good to me. The small spikes on it are around + 0.5 - +1.0 kPa. Maybe reduce the lag factor a bit and call it a day. The resulting PW variations are quite small : around 0.06ms.

Where does the MAP signal comes, onboard sensor or dedicated MAP sensor? If the latter, check the wiring going near this sensor/wires.

I would say that you are fine this way. But maybe you are more a perfectionist than me.

Sam

[billr]

I agree those oscillations are fairly minor, but they are noticeably there as compared to all other logs I have seen. Something isn't quite normal. Yeah, it has to be the OP's decision as to how far to pursue this; I agree on that too.

[tbaggins]

I guess I am a perfectionist. I really just want to know why it is happening, and then I can decide if it is something to worry about. And the MAP is a separate GM sensor that sits right above my main wiring loom on the firewall. I more inclined to think it is something with the MAF, and the regulator circuit is buffering the resulting voltage from the noise. If you look at the voltage signal from the MAF, it is the very noisy compared to the other two, and unhooking it made the TPS waveform worse at idle. I haven't started using the MAF, but I would like to soon. I will test the 5Vref today and unhooking the stock ECU, once I get my fan sorted out.

Thanks for the help and input.