So, I have a 1990 Toyota Pickup 22RE. It's been sitting for a while. I tried to clean everything up and put it back together. I got the truck running, but it had the surging idle. The first thing that I did was cover the hole inside the throttle body and the idle stabilized. So, I removed the throttle body and I removed the IACV. The Idle Air Control Valve looks fine. It looks relatively clean. I even removed the hose that goes back into the thermostat to make sure that it wasn't clogged too. Is there anything that I can do to fix the IAC valve besides just buying a new one? Or should I just resolve to buy a new one?

 

My son had a 1990 and a 93 that had this issue. The O-ring on the idle adjust screw can cause inconsistent idle. You adjust it, think it's good and later it needs to be reset, on and on.

On one of his trucks the IAC was all sludged up. We cleaned it and it worked for a while and we ended up getting a new one. The other "looked" ok but It was inconsistent. Again, replacing it fixed it. Both of these had a ton of miles on them.

They (IAC valve) do have to have good coolant flow through them. No air trapped inside.

If you have the A/C idle up valve adjusted too far, it will cause an idle surge. Any vacuum leak really can make you chase your tail but these two are common.