I don't think this is the cause of your misfire, but it seems your O2 sensor is acting like it's not getting hot enough to cycle like it should.
When you replaced the O2, did you put grease on the electrical connector? I've read that can cause it to malfunction, that it needs air to pass through there.
Do you have aftermarket headers?
Do you have one of those infrared pyrometer gizmos? If so, try checking if the exhaust (and by extension the O2 sensor) is getting to a normal temperature.


Separate issue: you should be getting fuel pressure as soon as the key is turned on. For it to wait until you bump the starter might be a bad fuel pump relay. Have you tried swapping relays as suggested by Patrick further up in the thread? But again that's probably not your misfire, assuming it holds fuel pressure when running and it sounds like it does.

quote Originally posted by Another One: I put the scope on the white wire between the IM and the coil and it is definitely missing pulses. I see the same thing with the scope on the disconnected tach filter wire. Not sure which wire is from the ECU to IM so if anyone knows, please let me know. Signal looks like it has switch bounce when going to ground and then spikes to around 60 volts positive. Not sure if that 60 volt spike is normal/acceptable or if it means the ECU is/has failed. I have tried a separate ECU but they are both 1988 with 150,000 miles plus. I checked for AC voltage at the alternator and the battery and the Fluke meter shows .002 so the alternator is good. Unfortunately it will be a few more weeks before I can try anything else as the 1986 MR2 needs attention now.

That mini-harness from the coil to the ICM is notorious for getting toasted over the years and often needs replacement.

[This message has been edited by armos (edited 06-15-2022).]