what should the isc reading be on mmcd

[maddog_187]

I was wondering what the isc reading should be at idle using mmcd or even a rough estimate.

I've got a bad idle that I am trying to figure out and slowly going through everything I can think of. I'm thinking I might have hooked up the isc wrong. I just swapped out my 90 isc with a 95 but not thinking when I went to extend my plug for it I just cut the wires not knowing there was two red wires so now I'm trying to find if I connected it right.

The reason I swapped the isc in the first place is someone sold me a 91 computer telling me it was a 90 so I never swapped pins 6 and 14 on the harness which one goes to the isc.

Any help would be appreciated!

 

[DSM1G90]

Check the resistance first between the four coils of the ISC with everything off with a multimeter. Any of those coils above 40 ohms have shorted out and a new ISC is needed.

You put the black probe from the meter in the middle of each of the three pins in the connector and read the pin's ohms on each side of that center pin.

 

[steve]

I was wondering what the isc reading should be at idle using mmcd or even a rough estimate.

Roughly 12-30 steps once the car is warmed up.

I've got a bad idle that I am trying to figure out and slowly going through everything I can think of. I'm thinking I might have hooked up the isc wrong. I just swapped out my 90 isc with a 95 but not thinking when I went to extend my plug for it I just cut the wires not knowing there was two red wires so now I'm trying to find if I connected it right.

Both of the center pins on the ISC have red wires since they are both the power connections for a set of windings. It doesn't matter which red wire you connect to which of pins 2 and 5.

The reason I swapped the isc in the first place is someone sold me a 91 computer telling me it was a 90 so I never swapped pins 6 and 14 on the harness which one goes to the isc.

Neither ECU pin 6 or 14 go to the ISC, one goes to the MAF (MAF reset) and the other to the IPS (Idle Position Switch) alco called the closed throttle position switch.

 

[maddog_187]

Thanks for all the help! I have checked the resistance and all of them are at 40 ohms.

Sorry you are right steve on the pins going to the closed throttle position switch. I am glad to hear that the red wires don't matter.

With the car cold right now the isc is reading around 90 to 100 steps. The last one I had in there was around 55.

What else should I be looking for if the idle is only 400 to 500 and dying?

I've checked timing, tried to adjust the biss (no matter if I screw it in all the way or all the way out there is no difference in idle), changed out computers my tps is showing 4.6 at idle the last I logged.