Idle problem


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From yesterday, I am working on wiring of my car.
Wiring is very messy like nest and no one knows which wire goes where.
So I decided to neat it myself because it is a very time consuming job and no mechanic will do it. They like easy money. :)

Now I saw some strange issue.
Everywhere on the internet, they say #10 provides ground contact to Injectors No 1 & 3 and #20 gives ground contact to Injectors No 2 & 4.

To my astonishment, connection was like this mind boggling.
Wires from #10 and #20 traveled separate for a while and then spliced together with one wire and then split again and connected to Injectors 1-3 & 2-4 respectively.

Am I hallucinating or what?

To my understanding, the ECU gives ground pulses to Injectors 1-3 & 2-4 via Pins #10 & #20.
#10 & #20 do not give ground signals simultaneously but only at appropriate times.
I mean to say, if #10 makes ground contact of Injectors 1&3, then at that time #20 will not... and vice versa.

If my knowledge is correct, then all my 4 injectors fire at the same time regardless of what pin (#10 or #20) from ECU is making the ground contact.

This way, 2 Injectors are always wasting fuel and contributing no part in combustion.
And this is the reason why my car is always running rich and all my Spark Plugs are Black.
And no matter what I do, change O2/ECT/IAT/MAP/TPS.... My rich running car problem will never solve.

Am I talking correct or not?
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I hate wiring.. would need to doublecheck the diagrams but I'm fairly sure your wiring is the way it was intended from factory.

The injectors are not controlled individually on this early EFI system. All four injectors fire together to get fuel into the chamber and then ignited in sequence by the distributor position. It's not a smart system but the technology at the time was fairly limited. Still works though :)


Fresh Recruit
Thanks bro for response and valuable info.
Below I am showing you the ECU pinout of my computer connected to my engine, which is 4EFTE.
Here I marked in RED that Pin #10 is providing pulse to Injectors 1&3 and pin #20 is giving pulse to Injectors 2&4.

My wiring shorted both #10 & #20 with a single wire and then all injectors are connected to that single wire.
Now, the problem is, when either #10 or #20 gives pulse, all the injectors spray at once, which is a waste of fuel.

There should be only 2 Injectors spray fuel with each ECU pin pulse.
This method is indeed not very economical but at least half way as compared to modern ECUs in which there is a separate pin from ECU dedicated for each Injector.

In my Case, the fuel economical is worse. Which can be make better4E-FTE 89661-10100 EP82 + EP91 ECU Pinout.jpg


Fairly sure they are pinned in two separate sets but the ECU only has one injector driver.

Could be wrong of course but that is my understanding of it.

Modern engines are very precise compared to the older generation so yes there are gains to be had if the technology was applied.