Mitsubishi 2.4 idle Adjustment

Ya the previous owner adjusted it. First thing I did was pull out the Iac/ISC to clean it. The thing was spotless. I pulled apart the throttle body enough to get a look at it and it seems to have been cleaned. The previous owner had done some work with the throttle body so I’m assuming it has been cleaned by the look of it. The car has 160k miles on it and the throttle body was clean besides some tarnishing on the passages. Here is what I did to get it running. I pulled out the screw (BISS not the throttle plate set screw) I wiped it down with throttle body cleaner the o-ring seemed fine. I put it back in the car all the way so it was closed off. I started the car and it idled around 1800rpm. I shutoff the car pulled the off the IAC/ISC and pulled the battery terminal. After a minute I put the battery terminal back on and started the car with the IAC/ISC unplugged, the car Idled back up to 1800rpm. I shut off the car plugged the IAC/ISC back in and started the car. This time it stared and idled around 400-500rpm. I backed the screw out until the idle was around 800rpm per my scan tool. We drove the car around with the scan tool plugged in and it seemded fine. I did notice the fuel trims are now back to around 0% where before it was reading +3-5% LTFT. We drove it around for about 30 minutes so this number may still go up. Its worth noting that the screw I’m talking about is the BISS – Base idle set screw, not the throttle plate screw and as far as I know that has not been touched. I have never worked on a Mitsubishi before mostly domestics and a few Toyotas, I have never come across this before. After we had it running I found this link: BISS Adjustment I’m not sure where these connectors are on his car but I may have a look when I go down there Sunday.

Ac does not cause the car to idle up, when I fist got in the car I noticed that. It would almost cause the car to stumble. After the adjustment the idle stays about the same when ac is on It may drop about 100rpm but not much. I think that may have been part of what was causing the code. I looked at the freeze frame data for the code and it was at idle fully warmed up and set around 500rpm, fuel trims were off as well. I’m thinking the IAC bottomed out when the ac came on and the car could no longer keep control of the idle so it set the code because the screw was out of adjustment. I’m not familiar with Mitsubishi and am not sure what the conditions are for that code to be set. He’s only had the car for about a month and thats the first time I’ve really got to look at it. He originally just asked me to reset the code because he thought it was for the gas cap but then I seen the P0505. He also mentioned his cruise control acting up but I’m not sure if it has anything to do with this. There is also supposedly an idle switch somewhere on the t/b that can cause similar problems.