I was replacing my ecu with an rtek equipped one when I noticed that there were some random wires leading away from the ecu area up into the area of the dash behind the logicon, i couldnt trace them. The wires werent attached to the ecu, but I found this jumper on one of the ECU plugs, and it is the same color as the other wires i found. Anybody have any clue what this could be? Maybe it has something to do with the fact that my car wont hold idle by itself?



TIA,

Tom

 

look up the ECU pinout in the FSM.

 

That far left, top row is pin 3I. It feeds 12vdc from the Main Relay to the ECU. How many wires are in that last top socket? Just the one red one? Then someone for some reason is feeding the ECU with a homemade circuit instead of the original wiring.

 

actually the pin is 3B, the connector is upside down. Its just that one wire in 3B

 

That's pin 3B, the START signal wire from the ignition switch. It tells the ECU when the key in is the START position and the engine is cranking. Maybe someone ran a new wire but it seems very unlikely you'd need to. This won't have anything to do with your idle.

 

It is an important wire though. When in START, the ECU sees this signal as long as the key is in START. In the START mode, the duty cycle of the fuel injectors is FIXED. The duty cycle is also dependent on how hot the engine is as seen by the water thermo sensor and the crank speed also has to be under 500 rpm.

If the water temp is 77*, then the duty cycle is set at approx 36ms. If the water temp is around 185*, then the duty cycle is set at approx 12ms.

Soooooooo, lets say your engine is at 185* but the water thermo sensor is broken/disfunctional, and it sees a temp of 77*. Then the ECU is going to inject at a duty cycle of 36ms instead of 12ms. Opps. Flooded engine.

Those are not the only duty cycles/temps involved. See the FUEL section of the training manual that is free and online courtesy of the NewZealander a couple of weeks ago.

The training manual is easier understood than what I just wrote. It also has a graph showing duty cycle during start vs water thermo temp sensor readings.

I think maybe, just maybe, the previous owner might have know a touch about the duty cycle during start and was experimenting????

So, now that I wrote that, how many wires are in 3B???????????????????????????????

 

Go here http://208.62.166.66:82/guest/shop_m...aining_manual/ and download Fuel and Emissions. Look at page 4-38.

 

there is only one wire in 3B, thanks for the link!

 

I'd experiment. Put a meter on 3B (back probe the connector when it's hooked up), and see if you see b/t 6-12vdc when you go to START. If you do see this, and when you let the key return to ON from START the voltage goes away, then I'd leave the thing as is.

Well, you might. I'd find out what and why this wire is buggered up and what it's going to and why the original wire is not in the back of 3B.

 

It's injector pulsewidth (measured in milliseconds), not duty cycle (a percentage). Noob...

 

Here's a jpg or two of that page out of the training manual. And while the NZ may possibly be right and I MIGHT have slightly screwed the pooch............NZ, go sit in the corner and SODER some 10gauge wire to your fuel pump. Hurrummph.
Picky kiwi.

 

could this signal at 3B be used as a fuel cut? the jumper i found is just one wire, and it looks like it USED to be connected to the brown wires i found coming out of the dash. I traced the brown wires and ended up pulling a switch out of my dash!