The idle speed motor in the xr8 doesn't work never has since ive owned the car. I can unplug it whilst the motor is running and there is no difference at all. Idle is currently set to approx 900rpm any lower than that and the eng will not run unless i manually open the throttle. on cold start up it hunts between 500rpm and approx 1500rpm for about 30 sec before its smooths out.

ive done continuity and resistance tests through pins 71, 83 and 97 and all come up at .9 ohms

resistance through the eng loom is .9ohms as is through the ecu loom

i have three v8 idle speed motors 2x AU's and an EF, i checked the resistance between them all and the:

AU Motors - 10.2ohms
EF Motor - 10.4

i couldn't find anything in the w/shop manual about testing these so im not sure if the above figures are good or bad.

the only other thing that i can think of is a crook ECU, but im unsure on how to test for that.

any info or pointers in the right direction is much appreciated.

cheers

I had a friend with an EF V8 that didn't idle well. I lent him a known good ISC I had, and there was no difference. Then I lent him a 4DED ECU which cured the problem. His mechanic told him that it is not the first one he's come across like that.

I have heard that this is a symptom of a common ECU fault in early EF V8's. I read somewhere it is a failed output driver.

I'll post the correct impedance range for the ISC tomorrow. My factory manual is at the workshop.

I can't make much sense of your post, but if you have tried a few ISCS, maybe try another ECU. The idle control circuits often fail.

I'm pretty sure the v8s are fussy with the idle adjustment though. Should say in the manual, but the procedure for setting the idle properly involves adjusting the TPS until it reads a certain voltage, then doing the idle with the TPS unplugged.

Goodluck.

Sorry about the delay in my reply. Stock impedance of ISC is 7 - 13 ohms. They also have an internal diode in series with the linear actuator coil, so resistance reads only one way.