For some reason, when my AC on, my RPM's will shoot to 900 then drop to 600 rhythmically every 2 seconds. Is this a tuning problem? Happens only at idle, when I am cruising RPM's are smooth as butter.

 

When the RPMs rise and fall do you hear the A/C compressor cycling? If you hear a prominent click sound every time the RPM drops it likely is your compressor cycling that's causing the RPM fluctuation. Two seconds between cycles usually means that the refrigerant is somewhat low.....

 

I Checked for that earlier and the compressor is staying on the entire time. I thought that was the problem at first too but seems like something else is causing it which is weird. Nothing related to the fan either because with the fan on and ac off the idle is smooth

 

Adjust your base idle air and ensure the IAC is around 10-15 steps.

GD

 

Does having IAC too high cause that? Right now it's at 22-24 at warm idle.

 

It's not what the computer is expecting, so..... possibly. Close the throttle stop and get the steps in the correct range. Might help, might not. Easy fix.

GD

 

I think I have fixed the issue. Will drive it again after later to see if it is fixed, but set my IAC A/C Delta steps to 0 for both the min and max and took it for a ride around the block and did not noticed the surging. So it was IAC related, but I still have no idea why.