I recently rebuilt my 95Z and replaced the IAC,ported the MAF, put on a new 52MM edelbrockTB. The car still has the A/C and I'm having a problem when the A/C compressor comes on. I know it puts a load on the engine, so it drops the idle a little, but I thought the idle would come back up even when the compressor is engaged. It does not, and the car idles around 750(target is 850). I can also see my dash lights flickering with the low RPM but my voltage is ok right at about 13-14. It just seems like something maybe like the IAC is not compensating for the load and it wont bring the idle back up. My cam is 218/224 .570/.565 on a 113, maybe a problem with idle because of the cam?Any help would be great.

 

What are the IAC counts at idle? Have you checked to make sure the IAC passageway is clear (possible left over metal from the casting process, dirt, debris, etc.)?

 

Don't know what the counts are(how do I figure that out). Also, I throughly cleaned the passages and the IAC is new. I've tried to turn the set screw for the blades out and it seemed to ignore the IAC because it wanted to idle too high all the time in drive and in gear. But the A/C did not seem to affect the idle as much when the blades were open that much.

 

I had this problem with my Impala, also, when I did an LT4 conversion and changed to a 58mm TB. I adjusted the TB blades, and made sure the IAC counts were appropriate. However, this did not resolve the problem.

In the PCM programming, there is a table that specifies how many IAC steps should be increased when the A/C compressor comes on, vs the A/C line pressure. I was able to get rid of this problem by up'ing the values in this table.

 

The counts (0-160) basically measure what position the IAC motor is in. Low counts mean that it is trying to close off the air coming in the passageway and high counts mean it's trying to let more air in. Your counts should be somewhere around 40 for optimal operation. You check these with Datamaster or Freescan (basically something that can read what the sensors are doing). Closing and opening the tb blades (using the set screw) is how you adjust the counts.

 

so basically i can try to fix this by adjusting the tables(tunercat) for the IAC steps or i can just keep adjusting the blades till it's right? If I adjust the tables, what numbers should I go to? Thanks for the help guys

 

Only adjust the blades to get the counts within spec (~30-50). If you can't get them within spec like that, then something else is wrong.

 

Right. Get the blades adjusted correctly first (and in spec). If you still have problems when the AC compressor comes on, you can try changing the values in the table I mentioned above.

 

thanks i'll give it a try and let you know what happens