I have a 1993 Z28 that I just got dyno tuned by ION. It runs awesome now becuase it is tuned correctly for WOT. However, I get a very rich mixture at idle. I have a CC306 on a 93 motor with LE heads. My map sensor voltage at idle is about 3.79 Volts and the counts are at 1 in closed loop. I get a code thrown every once in a while for map sensor voltage high vacuum low. I am thinking this is due to the cam and did a search with nothing helpful found. I have a vacuum canister for the brakes becuase they won't work very well. Has anyone had this problem? Or have a fix? All the vacuum lines are basically new.

 

Im on stock tune and have no issues with my brakes at all.. you have an intake leak somewhere? Vac leak of any kind?

 

Have you hooked up a vaccuum gauge to see how much you're pulling. You should be fine with a CC306. That high MAP voltage, by my loose interpretation, shows me that you're probably pulling somewhere in the area of 6-9 In/Hg. That's pretty low. Double check for a vaccuum leak. Are you using Comp R lifters?? If so you may want to double check your lash because on a similar setup on my car if they were anything past 1/16th lash they would cause a similar condition.

Your IAC seems to be functioning if it's count is at 1. What's your idle RPM at? You may want to try to close your throttle blades a little bit using the stop screw to try to get that IAC count up into the 40's range. How's the idle quality?? Is it searching for an idle or is it stable?? Any weird valvetrain noise?