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15+ Year Contributor
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- 852
- Aug 25, 2007
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Seattle area,
Washington
When plugging in a new Airtex or Standard Motor Products ISC to my 1990 harness, it runs backwards.
The pintle extends when you turn the key on, and retracts when you turn the key off. That’s backwards.
My original 1990 ISC does it right.
The pintle retracts when you turn the key on, and extends when you turn the key off.
I’ve looked through lots of ISC posts and haven’t found anybody else reporting this.
Seems I will have to reverse the polarity of one of the field coils to reverse the direction of the new motor, unless there is some other explanation.
But everybody says the wiring is the same for 90 vs 91 and later ISC’s.
Does anybody have an idea what’s going on? It just seems wrong.
The original 1990 ISC tests at 30 ohms on all 4 coil pins. I pulled it out of the car after a few episodes of galloping idle, high idle, and finally at the end it was making a loud clicking noise like a fuel pump whenever the ignition key is on. But it quit making that noise so that now I can do testing on it without any drama.
I’ve looked at the ISC drivers on the ECU board and they don’t show any physical damage, in fact they look brand new like fresh from the factory. . 1990.
The ECU board looks clean and nice from what I can see on top, capacitors were replaced by ECMtuning when they did the whole EPROM conversion and so-forth in 2015.
ECU is a 1990, with ECMlink V3.
Logs show ISC steps at 120 when I first turn the key on (engine cold), which then goes to 90 when I turn the key off. That I believe is normal. That 30 steps makes the pintle move about .040 to .060 inches, as near as I can measure it (about 1 to 1.5mm).
All 3 of the ISC’s are at about the same initial position when disconnected – with the pintle tip at about 1 and 11/32 inches out from the flange face.
All 3 of the ISC’s move about the same amount – just the direction is opposite!
The 2 new ISC’s I bought from Rock Auto for about $80 each and they look beautiful.
They are listed here:
http://www.rockauto.com/en/catalog/...,fuel+&+air,idle+air+control+(iac)+valve,6072
The pintle extends when you turn the key on, and retracts when you turn the key off. That’s backwards.
My original 1990 ISC does it right.
The pintle retracts when you turn the key on, and extends when you turn the key off.
I’ve looked through lots of ISC posts and haven’t found anybody else reporting this.
Seems I will have to reverse the polarity of one of the field coils to reverse the direction of the new motor, unless there is some other explanation.
But everybody says the wiring is the same for 90 vs 91 and later ISC’s.
Does anybody have an idea what’s going on? It just seems wrong.
The original 1990 ISC tests at 30 ohms on all 4 coil pins. I pulled it out of the car after a few episodes of galloping idle, high idle, and finally at the end it was making a loud clicking noise like a fuel pump whenever the ignition key is on. But it quit making that noise so that now I can do testing on it without any drama.
I’ve looked at the ISC drivers on the ECU board and they don’t show any physical damage, in fact they look brand new like fresh from the factory. . 1990.
The ECU board looks clean and nice from what I can see on top, capacitors were replaced by ECMtuning when they did the whole EPROM conversion and so-forth in 2015.
ECU is a 1990, with ECMlink V3.
Logs show ISC steps at 120 when I first turn the key on (engine cold), which then goes to 90 when I turn the key off. That I believe is normal. That 30 steps makes the pintle move about .040 to .060 inches, as near as I can measure it (about 1 to 1.5mm).
All 3 of the ISC’s are at about the same initial position when disconnected – with the pintle tip at about 1 and 11/32 inches out from the flange face.
All 3 of the ISC’s move about the same amount – just the direction is opposite!
The 2 new ISC’s I bought from Rock Auto for about $80 each and they look beautiful.
They are listed here:
http://www.rockauto.com/en/catalog/...,fuel+&+air,idle+air+control+(iac)+valve,6072