12a 84
Nikki Carburetor
GSL all stock

So about two weeks ago my car was idling ok and I was able to get it to 750/800 rpm. The throttle felt light and the engine had its natural brup brup rhythm. When I would rev it up to 6k and let it drop I could here the backfire being controlled by the shutter valve.

(Also keep in my I have never driven this car, so I don't know what it should sound like)

The engine was running ok though I had adjusted the idle mixture and idle speed screw, which meant I had to correct the throttle sensor, so I created the two light bulb test for check connector (B-25 LgY GY) I hooked the positive to the battery and one bulb to each wire. Now this is where I think I messed up because I forgot to disconnect the brown connector (B-18 short connector). I then revved it up above 3k at let it drop, in the process one bulb was constantly lit I’m pretty sure it was LgY wire (don't remember to clearly) no matter how much I turned it clockwise or counterclockwise both bulbs did not light up around 1~1.2k (B-18 is still connected)

Now this is other mistake. So I decided to turn the car off and I had left the testing light bulb circuit on the positive (terminal B alternator) thinking the car will completely turn off. I had completely taken out the key and car was still running because the fuel pump was apart this wiring schematic.

so the car was still running and (aftermarket) gauge lights were flickering (power surging low to high energy) so I quickly disconnected the positive from terminal B of the alternator.

This is where I think I burned out the ECU, though I did not conclude this until later.

I continued trying to test the throttle sensor and now no lights were on (with B-18 disconnected, but by now I don’t think it matters), and the engine sounded differently, and there was some clicking noises near the alternator. When I stepped on the throttle the pedal felt heavy it would rev up sluggishly, and no more natural rotary sounds or backfire. (I now think only one rotor is combusting properly...shutter valve stuck?)

I originally thought I messed up the two valves on the acv (port relief and switching) so I deleted the acv, as I have also given up on passing emissions (running classic plates). With that blocked off I rerouted the vacuum lines to help my MPG as much as I could since the solenoids for the acv were not needed anymore. Now my vacuum lines look like the image below, I also thought this would fix the issue with the engine running different. Now I know it made NO difference, which leaves me to believe that I messed up my emissions control unit. (https://www.rx7club.com/1st-generati...l-mod-1005150/)

Luckily some are still available and its coming in Monday.

Also I checked the throttle sensor and resistance seems to working properly as I pushed in the plunger.

PLEASE correct me if I’m wrong anywhere. I’m open to any thoughts, suggestions, opinions, and questions.

 

I figured the issue, part on the way. Im an idiot lol.

 

What was the issue?

 

The Emission Control Unit

It was pretty interesting because the ECU had gotten a large transistor and disc capacitor burnt out. When I received the new one I opened it up and looked at the same spot but there were 3 large transistors and no disc capacitor (A transistor in place of the disc capacitor). Which made me think, did the 84/85 ECU’s come which a slight improvement in ECU or was mine apart of an 85. When I looked up the ECU’s for 83 and before they looked slightly different. The original box also had N249 stamped so I know its 12a, but I can’t remember if the number sequence underneath N249 (Ex. K8T41471) is different. If so then it was a slightly different ECU for a 12a. The only reason I think it might be a different ECU is because the previous owner let me know that the engine was swapped in from one she had crashed before (so maybe she swapped the ECU’s)(or swapped a later year ECU inside the same casing, if possible). Also the bolt holes for the ECU cover panel had their previous removal marks. Maybe I’m just thinking about to much

As well when I had previously tried to adjust the throttle sensor there was no effect on idle no matter how much adjustment. Also It sounded more like large street port, though everything on my car is stock.

Anyways I have the right one in now and a note to myself DISCONNECT the Throttle sensor tester before turning the car off

Now its idling normal (at least I think it is)

When I adjust the throttle sensor I was actually thinking of posting a video to get some feedback if it sounds normal.

 

This is really interesting. I've been chasing my tail with an throttle and timing advance issue on my 80 and now you have me thinking to check the ecu, which previously I had ruled out. I've made adjustments to many components and nothing changes. The issue comes and goes and it could possibly be an ecu thats on its way out. I'm glad I ran across this thread!

 

Thats crazy lol... In my experience with electrical components sometimes changing a simple resistor effects the entirety of a circuit, especially if its old. Something might be out of its tolerance zone as well... I got my ECU for about 70$, but that was for an 84. I couldn't find a-lot of info on the ECU’s when I was figuring out my problem.

If you can? I’d like to know if there was an issue with yours.

 

I will definitely keep you updated on what I find.