ECU burning out ISC motor?

[moonraker]

for many years i have been noticing the idle surge problems on and off on my 2g 6-bolt swapped-GST. i replaced the ISC motor about a year back and it worked fine for a bit, but about a month later, the same problems arose. i ran it for a couple of months then had to work on it. its back on the streets but has that same idle surge problem. i took out and tested the ISC with an ohm-meter and got 40 ohms across the board, proving that it is a bad ISC motor again. i then turned the car ignition on and tested the voltage coming through the harness by putting the postive in slots 2 and 5 and negative in slots 3 and 6, resulting with 12 volts... i believe this is too much? or am i reading 12 volts because an accurate reading can only be seen when plugged in? now, the previous owners of the vehicle had the biggest rig on the ECU wireing for the swap and i worry they may have wired it wrong. could this be causing too much voltage to go to the ISC?

let me know what you think please,
george

 

[yokotabrat]

40 ohms doesn't necessarily mean the isc is bad. If you have one of the newer iscs like what's sold on dsmisc.com, then they are designed with a higher impedance than the original iscs that sit around 30 ohms. Could be a leak that just developed, have you done a pressure test? Maybe the FIAV is bad on the throttle body. Throttle cable is adjusted correctly? Has the problem ever gone away? If the previous isc was shorted (less than 10 ohms) it could have damaged the drivers that control the isc in the ecu.

 

[steve]

i then turned the car ignition on and tested the voltage coming through the harness by putting the postive in slots 2 and 5 and negative in slots 3 and 6, resulting with 12 volts... i believe this is too much? or am i reading 12 volts because an accurate reading can only be seen when plugged in?

None of the other pins in the ISC connector are a valid ground reference.

Pins 2 and 5 are the incoming battery voltage but the other pins are the lines the ECU pulls low to make current flow in the ISC coils. They need to be current limited or they will blow the drivers in the ECU. Normally the ISC coil does this due to it's DC resistance.

Sticking your meter across the connector shouldn't read anything unless the ECU is trying to active that coil while your measuring. Most modern multimeters shouldn't pass any current while measuring voltage but depending on how your meter is working could cause damage to the ECU by testing in this manner.

I agree with Yoko, I don't think you have any indication that the problem is ISC related.

Steve