My other car is 97 Miata. It is far beyond stock now, but when it ran the original CPU, I could bridge the ten and ground ports in the diagnostic plug in the engine bay and then set base timing.

With this 87 NA FC, it just says to let it warm up, idle, and it should be at 750 rpm. Is there anything to lock it at that RPM? When mine is idling, the timing seems to be jumping around a lot along with the RPM changing. I thought that it might be the TPS is seeing movement, but it is stable when looked at with a multimeter.

I want to get everything on it and make sure it is stable before I switch over to Megasquirt

 

You can't lock it at 750 exactly, and some of that inconsistency might be from timing being off. Bit of a vicious circle.

Anyways, the FSM says 750 but really you should just have it under 1000rpm and jumper the initial set connector. This is the two pin green connector by the drivers side headlight. All this does is tell the ECU to not intervene in the idle and not advance the timing. The reason the FSM says it needs to be 750 is that that is the stock idle speed and consequently the ECU isn't trying to advance the timing at idle. But under 1000 and with the connector jumpered gives the same result.

 

Just to confirm, this plug here?

 

That's the one

 

that plug there is the 1987 TEN (Test ENable) and Ground