any one know what the iac should be reading on a 89 305 tbi when engine is warm and at idle (775rpms). i'm using winaldl if that helps. or even what its suppose to read when cold

 

According to a book I'm reading on Chevy FI the reading should be 7-20. The full range is 0-255 with zero being fully closed and 255 being wide open.

I have the same engine (305 w/ TBI) and just started using WinALDL to capture data from the ECM. The values I'm seeing at hot idle are more in the 33-44 range. I can send you an Excel spreadsheet of the captured data if you think it would help.

I should mention that I'm running an open element air cleaner, have done most of the ultimate TBI mods (ridge removed & polished, injector pod spacer, and trimmed throttle shafts) and running a custom chip.

Again, according to that book a low IAC count indicates a vacuum leak or an improperly adjusted Minimum Air setting. I guess a higher value might indicate a partially blocked IAC air circuit (carbon buildup, etc.). My TBI was thoroughly cleaned when the mods were done, so that is not a concern in my case because the engine idles just fine.