1G Idle speed sensor wiring

[90EclipsePos]

Can somebody shed some light on wiring for the ISC.

So I've been chasing an idle issue for years after rebuilding my engine and having numerous things go wrong. I've tested the ISC, it ohms out fine, I have 2 out of 3 ISC's that ohm out good. When I get to unbolting it from the throttle body to test if it extends and retracts good, It does the opposite like the plugs are wrong on the ecu.

Now the part that is throwing me off on this is the fact the other day I double checked my ECU and my pins 6 & 14 were reversed so I swapped them back.

Pin 6 should be Green and 14 Green/White this is correct right?

After switching the wires my ECU shows my Idle switch working which it didn't before I swapped the wires. So the wires should be correct. So what else would cause it to work opposite?

At one time I cut my ISC plug to extend it and didn't realize that it had 2 red wires. Is it possible that if I got them reversed it would cause it to act that way?

 

[steve]

If you have a 90 ECU, pin 6 is the Green wire from the IPS and pin 14 is the Green/White wire for the MAF reset line.

Those switch on 91+ ECU's.

The ISC wiring is also slightly different between 90 and 91+ cars. Pins 4 and 6 at the ISC are swapped between the two.

Since the connectors (90 pigtail vs 91+ connector) are different between the early and later ISC's it's hard to say if this is a connector difference or if the 90 ECU pulses the ISC coils in a different order than the later ECUs without some code inspection and experimentation.

The two red wires both feed battery voltage in parallel to the ISC coils so swapping them doesn't make a difference.

 

[90EclipsePos]

What I don't understand is I'm using the stock plug from my 90 and just extended the wires then matched the colors exact same way. So what could cause it to be working opposite if my ecu wires are right?

 

[90EclipsePos]

So I double checked today to make sure when I extended my isc wires that I didn't mess up and mix up wires. Everything checks out. My plug matches what a 90 plug should be. My ecu wires are correct. Is it possible for my isc drives in my ecu could be bad and causing this?

 

[2gmitsueclipse]

At the very least, an inspection of the ECU could rule out a failed driver. Just be aware that if the driver is damaged, it may have also damaged traces as well. For more information, check out the following link:

https://www.ecmtuning.com/wiki/driver01#blown_isc_driver

 

[90EclipsePos]

I'll double check it tomorrow and see if I notice any. The ecu was rebuilt not long ago from motoguys garage. So I haven't suspected it thinking it should be fine

 

[2gmitsueclipse]

A failure may not have been solely due to the ECU itself. Here is an additional helpful ink:

http://www.dsmtuners.com/threads/troubleshooting-fried-ecu-components.116585/

 

[90EclipsePos]

Some of that is beyond my skill set. Lol It is definitely helpful though. The odd part to me is when I change my ecu wires the way I should to run a 91 ecu. My isc works the way it should. Could something in the ecu been installed incorrectly? I serious doubt it could happen, but is it possible?

 

[jim95redgsx]

https://www.ecmtuning.com/wiki/idlesurge
Scroll down to Throttle Body Problems and read the 5th paragraph under that.

"Using a 90 harness with a 91+ ISC. or vice versa, will cause the ISC to operate backwards."

Is it possible that you have a 91+ ISC. It seems that the only difference between the 90 and 91+ ISC's is that the #4 pin (white wire) and the #6 pin (black wire) are swapped (on the ISC connector). Try swapping the white and black wires.

Jim

 

[steve]

Lets see a picture of the ECU circuit board to make sure of what you have. An overall picture and a close up of the driver section would be great. I've seen many cases of bad M5269L driver ICs where there the chip wasn't burnt up so it's not always the case that you can look and know.

If your ISC steps in and out correctly with the 91 wiring I would suspect the board before a bad driver.

 

[90EclipsePos]

I'll get some pictures tonight I'm also going to swap in my stock ecu and see if it operates the same way and that should help narrow it down a little more. But I'll get some pics tonight and post them.

 

[2gmitsueclipse]

If you choose to swap the ECU, ensure that you are running the stock fuel pressure and swap out for stock fuel injectors.

 

[90EclipsePos]

If you choose to swap the ECU, ensure that you are running the stock fuel pressure and swap out for stock fuel injectors.

I should be able to adjust my maft for my injectors instead of swapping them out right? Also I should be fine either way since to test the isc I only turn the ignition to "on" instead of starting right?

 

[2gmitsueclipse]

Your other ECU must have been stock then! Yes, you shouldn't have to make any adjustments then.

 

[90EclipsePos]

Okay so swapping ecu did nothing same issue.
Swapping both reds around did nothing.

Attached are pics of the ECU, shouldn't matter now but still putting them on. Next I'll take pictures of ECU wires to confirm they are correct.

Any other ideas out there? It makes no sense to me at the moment. I will also try swapping black and white wires just in case even though they match up on the harness.

Sorry would have added more pics of ECU but picture size was too large.

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[90EclipsePos]

Here are the pics for the wiring to the ecu.

 

[90EclipsePos]

Tonight I will try swapping black and white wires and see if that helps. Other then that I'm about it off ideas. I'll see about making a video also if it doesn't work.

 

[1990TSIAWDTALON]

I run a 91 TB and sensors and those are the only 2 wires I had to swap and my ISC works normal. Just the black and white wires needed swapped.

I am running a 90 ecu.

 

[90EclipsePos]

It vibrates for a fraction of a second with the black and white wires swapped. So what in the world would cause it to work correctly if my pin 6 and 14 are swiped on the ecu? Ecm tuning says those wires have nothing to do with the isc But some how it causes my isc to work one way or the other?

So to recap 90 ecu, 90 isc stock plug and wiring all colors match on the plugs. Still trying to get a video to show swapping the ecu wires causes it to operate differently.