Not sure if my IAC on my '92 740 Regina has failed, or I have other issues.

On start, it seems normal. Then after 10-20 seconds, the IAC opens, and it idles to ~2000RPM. With the IAC plugged in, it idles at ~2000RPM, pulling the plug causes the idle to drop to 500RPM. Goosing the throttle does not cause it to kick down. Happens when hot and cold.

I tried cleaning it, but no joy.

I verified that it opens and closes (removed the hoses, plugged the one going to the intake manifold, unplugged/re-plugged the IAC multiple times, felt & heard it working). When I plug it in, I can hear & feel it open, but it fails to close at the proper RPM.

This makes me wonder if something else is wrong: That maybe the IAC is OK, it just isn't getting the signal to close..?

Anyway, assuming the IAC is faulty, it occurred to me that the only significant difference between the Regina and the Bosch was the plug. Both are two wire and take the same size hoses. The only difference seems the Regina is a piston and the Bosch is a rotating cylinder. I'm going to try the Bosch out with some jumpers. It conveniently has positive and negative marks on the valve electrical plug, and I cut the female plug off a junk 240 when I grabbed it's IAC (same as my other 740/Bosch), so all I have to do is establish the positive lead from the car, and I can jumper it.

If that works, it should save people some money as the Regina IAC is kinda pricey new, and harder to find used.

But, if someone can give me some ideas as to whether it's even getting a proper signal, that would be great.

TIA

Dave

 

Update: Trying to jumper from the Regina IAC plug to the Bosch IAC was sporty, given that there's not much room, the wiring harness has very little slack, it's hard to see, and you have to do it with the engine running. But!

Pretty sure the Bosch IAC will work on a Regina if you adapt and wire the plug right.

Before I sacrifice the Regina IAC though, I'm going to verify that it is indeed dead, as what I am going to do will surely render it totally inoperable. Pix to follow.