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.

 

Pardon my 'Yota Ignorance, but what is the A/C idle? I've not adjust anything. So, even though I put a piece of tape over the hole in the throttle body and it ran correctly (I think) it could still be something else?

 

listed in the pic as A/C idle up adjustment screw

 

That's an excellent pic/diagram. Thanks for posting that. I haven't had a 22RE for a long time so the visual reference really helps.

Not sure what hole you covered with tape so I don't know what to offer about that.

As far as the A/C idle up, you can see it in the pic above. The hex shaped knob with the slot in it and with the spring under it, adjusts the idle speed when your A/C is on and the compressor clutch is engaged. If you go too far, it will surge.

After all these years the diaphragm inside may have failed also. It's no longer available. There are a few posts on how to adapt one from a more modern Toyota. It's slightly different but works the same. Just another thing that can cause idle surging.

 

That's a great picture/diagram! Thank you so much for posting that!! I know the piece to which you are referring now. However, I really don't know what it does. I'll have to look into that.

 

Ah! OK. That makes sense. Thank you for the info. The hole is just inside the opening of the throttle body. I just placed a piece of tape over it long enough to lead outside so that I could reinstall the intake tube and the piece of tape not get sucked into the throtte body