Here is one that has me stumped. I recently put a rebuilt 3.0 in my 4runner. Also installed a magnaflow cat and Black Widow exhaust. If I have the a/c on and idling at a red light, intermittently when I try to take off, there will be no power at all, truck will barely move. If depress clutch, it will rev up. When I turn the a/c off, i immediately have power back. Any ideas???
Thanks in advance

 

Could it be your ac idle up valve? When you switch the ac on while idling, do your RPM decrease? I had my idle up valves deleted but after finding and fixing the issue was with the ac that the PO told me was unfixable, I charged up the ac and got it cooling. I found out quickly though that I was going to have to reinstall the idle up switching valve. Had very similar symptoms. My RPM would fall to an uncomfortably low speed with the truck in N idling. After plumbing the valve back in I saw that my RPM was not just a little higher with the AC on than with it off.

 

Idle still bumps up a couple hundred rpm when a/c is turned on.

 

Does the ac cool OK while you are stopped at said red light? I hope it's not your compressor trying to seize up on you.

 

Didn't notice a drop in air temp. I will check that next time out. Compressor was replaced when I did the rebuilt motor, soI hope that isn't an issue