Breze84

Have a question. I got a 2000 Chevy Lumina with 163K miles and its got a issue I want to get a opinion on. Im pretty well mechanically inclined when it comes to cars but im not a career wrencher. So about a couple months ago I was getting a random misfire in every cylinder when the car would warm up under load, Mostly at lower speeds or when the car shifted and the R's would drop. I test my ICM, Coilpacks ect and everything checked out. So I tossed on a new set of wires and plugs and cleaned my IAC. The hardest part about it was I wasnt getting a MIL on the dash. So I took it to a mechanic guy I know to have him toss it on his scanner for live data. He said everything seemed normal and replaced the TPS for me because he said it showed a code. "No biggie" But the car was still having the issue and said he was leaning towards the PCM being bad possibly. I was very skeptical about this and just limped the car around for a bit until I had a chance to really get into it. So I was driving it last week and noticed that when this issue would happen my Volt light on the dash would come on and my lights seemed to dim a bit. I just tossed in a new Interstate battery a few months back so I knew it wasnt the battery. So i checked the output of the Alternator. I was getting 13.8-14.0V when the car was in park. But once I put it under load it dropped down to around 11.2V. So It dawned on me that maybe I had a couple bad diodes in it and it couldnt produce the power to keep either my fuel or ign up to par and it was cutting out. I changed the Alternator and Serpentine belt, And boom the random misfires went away and the car drove excellent for the past 2 days. So now yesterday I started the car up to take a ride somewhere and I noticed my Idle was high around 1500 and wasnt coming down. I put the car in drive and it would drop to 1100. Still a little high! I gave the car a quick rev and it seemed to drop back to normal which is around 800 or so. Did my thing, went home and shut the car off. Came out a little later started the car up and it died instantly on 3 attempts. I then started it a little gas and it didnt die, BUT the RPM's were chugging around 500 and my A/C clutch seemed to keep engaging and disengaging loudly until I reved the car up. My check engine light came on and I had a P0506 code, So I check for any Vac leaks and I had one little one up by the EVAP tube where it goes from the PCV valve in the front valve cover to the Intake neck right after the TB. I fixed that lamely enough to where I wasnt getting a leak anymore and pulled the IAC out and cleaned it up and pulled the PCM/BAT fuse to clear the cell. The car was still having the issue so I tried doing a idle relearn which was bringing the RPM up to 1500 back down to around 750 or so until it idled on its own for a min, Put it in drive and let it idle for a min, Put the A/C on and let it idle for a min and it seemed to be good until I shut the car off and started back up again. Same issue as before! So I put a new IAC in and did the same thing again and its not fixing the issue, The MIL came back... What do you think is going on? I have no vac leaks at all...