I have a little problem That I'm hoping to get information on. To give some background, my '91 F-150 w/302 had an idling problem. In the morning, it would go to it's usual high idle for warm up and then gradually drop rpm's 'til it died. Crank it again and it would idle ok (at best). I fished around and changed a few things; MAP sensor, TP sensor, O2 sensor. None of these cured the problem. I dug some more and found my idle air control valve restricted by carbon, that of which explained the bad idling. Now I have a steady idle, but my low idle is running higher than it should be (850 to 1000 at low idle). I tried adjusting the idle screw on the thottle body but that didn't help.
The book tells me I should get about 10.5 volts to the IAC, but I,m getting almost 12.0 volts. Could this strong signal be a problem with it's normal operation. If so, how can I correct it.
It's not causing any problems, other than burning too much gas at idle, but any information would be helpful.

thanks

 

I think 12 is what you're suppose to get. 850-1000rpm, I haven't the foggiest. Maybe the computer needs to "learn" the new IAC. I don't think the eec IV can do that though. Maybe the IAC and TB ports need a thorough cleaning. Maybe you have a tiny vacuum leak?