pwoolsey

I have a 1993 22re 4x4 that runs down the road fine. But I can’t get a constant smooth idle on it. I have tried adjusting the fuel mixture and idle screw but it does fine for awhile then the idle drops real low an erratic. It has ac but seems to run ok with it on. I am including a picture of an electric plug that I can’t figure where it connects. Thanks for any suggestions you may have.

2ToyGuy

I'm not sure about the plug, but as to your idle troubles: First thing I can SEE right off is the crack in the big air tube between the AFM and TB. That may well be leaking air in. You really should seal any cracks in that tube up, or replace them. Those flexible corner pieces are readily available, and fairly inexpensive.
Another thing that could be causing troubles is the PCV return line isn't connected. It looks like it was either pulled off for the picture, or cut in half at some point. It's a shaped hose, but very reasonably priced, and readily available.
Speaking of, when was the last time you replaced the PCV, and the grommet that holds it in the valve cover? Definitely use OEM, not some cheapo, auto parts no-name PCV, and for SURE replace the grommet. It gets "old" and brittle pretty fast, and when you go to pull the PCV, it's common for it to break up into chunks and come out. Watch that the chunks don't fall inside the head! Many folks replace the grommet while they have the valve cover off for setting the valve lash, and replacing the valve cover gaskets. That way the chunks of grommet can't fall down into the head.
Another task you might consider doing, BTW, if it's been a while since it was done last. The valve lash, and valve cover gaskets. That includes the 2 halfmoon pieces, front and rear, and the grommets for the acorn nuts that hold the valve cover on.

What do you have the idle set to? It's supposed to be about 800-850. If it's much above 1000 RPM, the computer is programmed to cut off the injectors when you step on the brake, then allow them to function again when the RPM drops below the "trigger" RPM of about 1100. Toyota figured that if you're stepping on the brake, you don't want the RPMs above idle, so to save fuel, the ECU shuts off the injectors. If your RPM is set too high, when you step on the brakes, the RPMs will drop, then rise back up, then drop, etc.
Speaking of the idle, did you check the idle adjust screw's o-ring? After 30 years plus, it is brittle, and may very well disintegrate, falling down into the air passage, and causing problems. You need to screw the idle adjust screw all the way in until it stops, counting the turns it takes. Then unscrew it all the way out to inspect the o-ring. It's a very common size, and very very available. You can also, while the IAS is out, clean the air passages. A little carb cleaner, or brake cleaner and you're good to go. When you put the new o-ring on, give it a light coating of Vaseline, or silicon dielectric grease. It will make it last much longer, and get a better seal. Then you can screw it back in to the bottom, and back it out the number of turns you counted earlier. It may not be right, but it's a starting point.
Make sure the TPS is adjusted correctly, in accordance with the FSM. Make sure the AFM ohms out according to the FSM as well. Check out the IACV too. If it's not closing down properly, it will allow air in when it shouldn't.

Make sure your timing is set correctly. 5° BTDC, with a jumper between TE1, and E1, in the test connector on the side of the fuse box in the engine compartment. Once it's set properly, pull the jumper out, and verify it climbs up to about 12° BTDC. The jumper is pretty costly. At least 1/2 cent for a paperclip Once the timing is set, double check the idle again. Ensure it's set correctly.

When was the last time it got a tune up? Plugs, wires, distributor cap and rotor, air filter, and so forth. They all can cause idle problems.

I hope something in all my babbling may help a little. Let us know how things go for you.
Pat☺