Hello! I pride myself in being somewhat knowledgable with GM EFI systems, but the Northstar motor in some ways is quite different from other motors that I have dealt with. I've been asked by a coworker with a '95 Eldorado to help him figure out what is wrong with his car. It idles too high, most of the time. It is to the point where it is making it difficult for him to stop and shift in and out of gear.
When the ignition is turned off, there is a fairly loud buzzing noise for several seconds, that we tracked down to an electrical component bolted to the throttle body. We're guessing that this is related to the idle problem. It has a 4-position weatherpack connector and looks like a solenoid of sorts. The rod of the solenoid looks like it affects the position of the throttle.. kind of like the fast idle solenoid on old carburetor-equipped motors.
Anyway, while this module is making its fitful buzzing sound, if you pull or push on the solenoid rod it goes quiet. release it and it is loud again. This sound continues for up to 10 seconds if left untouched. Hew said that if he feathers the throttle just right, the idle speed will settle down and he can comfortably shift. I imagine this is doing the same thing as when I fiddle with the rod by hand.
If this module is unplugged while the motor is running, the idle goes even higher and seems to "hunt". I had hoped that he could drive without this module connected until I found out if it is indeed faulty but that doesn't look like a viable option.
So first of all, what is this gizmo? Is this used in place of the IAC that is common on other GM EFI systems? is it likely that if this component is faulty, that the idle would be affected in the way I described it? What are the chances that this solenoid is actually OK, and what ever circuit drives it could be the culprit?
TIA, Kevin Spears