Re-adjusting / Resetting the Idle Air Control / IAC valve on the Toyota 22RE motor in 89-95 Pickup

[@ray5961]

** UPDATE Jan 25th, 2024: 3.5 to 3.75 TURNS SEEMS TO WORK BEST. I tested 5.0 and 4.5 turns and also 3.0 and 4.0 turns (counter clockwise from fully seated) and 3.5 to 3.75 turns seems to work best. 3.0 turns seems to be too restrictive, while 4.0 seems to be just a bit too far open. I'm currently testing 3.5 turns (as of 9-13-2025) and will post any further updates here.

[@cbh148]

Excited to see the video on the potentiometer that presumably is altering the TPS or AFM signal back to the ECU. Also, very good to know that 5 turns out seems to be a solid IAC valve seat setting. Haven't seen that TCCS manual before but I've just looked it up and downloaded it as I like learning about Toyota's control strategies of these golden era vehicles.

[@ray5961]

Yeah, the TCCS manual is very well written and very helpful. It covers later model Toyota engines as well as our engines, but as far as the 22RE it really does a fantastic job of explaining what the ECU and everything (e.g. AFM) is doing when it comes to engine and fuel management. I'll add the link for the PDF in the description of the video in the next day or two. I should also have a video on the throttle body switch & potentiometer stuff pretty soon as well. You've got the right idea, but I'm not using the TPS or AFM signals because they are primarily involved in closed loop trim operation, whereas the issue I was trying to address is mainly during open loop operation. Basically the potentiometer I showed is modifying the engine coolant (THW) input signal to the ECU, which tricks the ECU into thinking the motor is cold / still warming up and thus it widens the fuel injector duration to provide additional fuel to the motor (based on that chart which I showed in the video there). I have things configured so that the potentiometer allows me to either totally disable this feature or widen the injector duration by as much as [roughly] 180% or so. As you can imagine, changing the THW signal has an immediate and dramatic impact on A/F ratio. The potentiometer is 5K, which gives a fairly wide range of control, but also leaves plenty of fine grain resolution. The micro switch enables the circuit only at wide open throttle (WOT), since the ECU is normally running in closed loop mode most of the time when cruising at partial throttle. The setup basically works as a sort of fuel dump during rapid transition into WOT, which removes any acceleration hesitation or lag (where the ECU momentarily is confused and ends up leaving the motor in a lean fuel condition too long); this allows the motor to cruise at a slightly leaner air/fuel ratio 99% of the time (for good gas mileage), but when you need to merge lanes or accelerate up a hill or something, it forces the ECU immediately into a richer A/F ratio that is best for max power (and the dial on the dash allows you to fine tune what that A/F ratio is). On a modified / higher performance 22RE motor, it really helps a lot, since often times the stock ECU is operating on the edge of what it can fully understand. I'll have more information on it very soon.

[@cbh148]

@@ray5961 Excellent! Didn’t realize TPS signal (the linear position one, not the IDL binary signal) was only a closed loop ordeal. I knew most ecu’s of this vintage switch to open loop at heavy amounts of throttle, but that threshold between what amount of throttle is heavy and what isn’t has always been sorta arbitrary to me.

[@ray5961]

@@cbh148 Yeah as near as I can figure the ECU runs mostly closed loop unless you go wide open throttle. I'm not 100% sure what Toyota has going exactly, but it seems like that's sort of the deal.

[@kassie9173]

Thanks very much for your great videos! I'm learning so much from them! A bit unrelated, but I was wondering if you adjust your idle stop screw so it just touches the throttle stop lever, or do you turn in the idle stop screw 1/4 turn to always keep the throttle body butterfly open a tiny amount? Also, when my engine is completely warmed up and I adjust the idle speed to about 850 RPM it never returns to the same idle speed I adjusted it to after operating the throttle for a few seconds and releasing it. I have my dash pot adjusted to close the throttle completely at about the 2 second mark and there's no binding whatsoever. The idle speed always returns to about 100 RPM higher than where I set it at. If I set my initial idle speed to 750 RPM to compensate, it sometimes goes down to 650 RPM after operating the throttle, or sometimes it still remains higher than I want it to! The idle speed adjustment screw has a new 0-ring and is sealing well. The MAF and EGR systems are all within factory specs, the MAF door is moving freely and the TPS is adjusted properly. Just installed new Denso plugs and OEM distributer cap, rotor and plug wires, and the engine is timed at 5 degrees BTDC with the jumper in place. Without the jumper it moves to about 12 degrees BTDC at idle. Do you have any suggestions as to where I should look next to fix this idle issue? Thanks in advance! 1990 Toyota Pickup with 22RE motor.

[@ray5961]

I can't remember exactly on the screw related to the throttle body butterfly valve, but whatever the factory manual shows, that's how I did it. I believe it's a deal where you use a feeler gauge, but not sure off the top of my head. Try resetting the ECU by pulling out the 15A EFI fuse for 5 minutes. Sometimes that can reset the trim data and help smooth out idle a bit.

[@kassie9173]

@@ray5961 Thanks Ray! The FSM says to adjust it so it just touches the throttle stop lever, but lots of people in the forums say to go 1/4 turn further so the butterfly doesn't completely close. I currently have it set 1/4 turn in, but hesitate to back it off or I'll have to re-adjust the TCS. I'll pull the fuse and see what happens. Thanks!

[@ray5961]

@@kassie9173 I have it set according to the FSM where it touches and the TPS is adjusted from there. The adjustment on the TPS is everything to the ECU so I'd go with what Toyota says not the forums in this case

[@kassie9173]

@@ray5961 Perfect, I'll give it a go this weekend!

[@ray5961]

@@kassie9173 Let me know how it goes. As you already know, the precise adjustment of the TPS is of paramount importance to the entire ECU system, fuel management, etc. The throttle plate should be closed when the TPS says it's closed, so that the idle adjustment screw and also the IAC valve can do their jobs without additional air slipping under the butterfly valve. Any bypass air needed by the motor when at idle (i.e. foot off the throttle) should be controlled strictly by the idle adjustment screw, which is a passage which allows air to slip around the closed throttle plate... so what would the purpose of the "slight crack" on the throttle plate that the forums are suggesting? I can't understand what it would benefit, given the idle screw is providing that same pathway for air, you know? Also, in terms of the warm up and enrichment phase when cold, the air slipping under the throttle plate would also be skewing the entire logic on the IAC stuff. Most likely this all would only serve to lean out idle, which isn't a good thing in terms of idle stability. In fact, you can demonstrate this by clicking the AFM spring 1 click richer and you'll notice that idle suddenly is much smoother and more stable (but gas mileage, look out). You can also use the adjustment screw on the AFM (which provides a small bypass channel for un-metered air). Turning this down (clockwise) will limit un-metered air and thus richen the mixture at idle (and across the board to some degree). Without a wide band controller and gauge it's very difficult to see all this taking place in real time. However, effectively a lot of these small adjustments are aiming to help get the ECU back to a more or less idle air/fuel mixture when you suddenly come off throttle. If your adjustments toss the air/fuel ratio to the lean side, then the ECU will have to slowly pull it back richer at idle. This will manifest itself as low or unstable idle until the ECU trims things back to 14.7:1 a/f ratio. If you are adjusted more to the rich side, then idle will seem to always be higher than normal and slowly settle down. This is because the a/f ratio will drop back around more like 12.5:1 and then slowly climb back up. More gas = higher RPM's, until it settles things back down around 14.7:1 and your idle goes to where you set it with the idle screw. Also keep in mind we are dealing with OBD1 here... 1990 ECU programming. You're never going to get the 22RE to idle like a Rolls Royce, no matter how many adjustments you make. There's always going to be some slight fishing around near idle when you come to a stop, unless maybe you have a bone stock 22RE with all the smog stuff functioning perfectly on a brand new rebuilt motor and you've got an automatic transmission in the mix to smooth things out with a torque converter, etc. Anyway, definitely go with FSM specs on the TPS and throttle plate.

[@ShawnMahoney-m3t]

This looks like how mine runs. Is the 2k rpm at cold start concerning?

[@ShawnMahoney-m3t]

This looks like how mine runs. Is the 2k rpm at cold start concerning? Seems high to me

[@ray5961]

depends on how cold it is outside 2K is okay as long as it starts to drop down within a minute. Check the flow through your hoses going to and from the IAC valve, also coolant level in the system. Make sure there's no air in there any where.

[@joshuawilliams2409]

Ray, 22RE (86 4Runner) my cold start idle suddenly staying around 1000. Used to be around 1300 on start and settle to 950ish after couple minutes, per the IACV. Idle is smooth, no fluctuations, not rough. Idle just doesn’t change like you’d expect. I did disconnect and reconnect battery…could that have messed with ECU? Thank you for any info.

[@ray5961]

Yeah, when you disconnect the battery, it will reset the ECU. It usually takes about a week for the ECU to re-learn everything. Check to make sure the coolant hoses running to and from your IAC valve are warming up and not blocked or anything.

[@glenmaney-r6e]

I have a 95 Tacoma. 2.7l it started idling up and down. So I changed the TPS and cleaned out the throttle body which was full of carbon, that seemed to fix my problems but a few days later I developed a high idle so I decided to take the throttle body back off and clean out the IAC it also was full of carbon. Put it all back together and it ran great for a couple hours went to town and back and immediately I experience rough idling and stalling and it’s been like that since and I can’t get it back to running correctly or idle right. Cold starts are very rough and if I give it gas peddle and let it run for a few mins it’s fine after it warms up or if I turn the dashpot screw in to give it more throttle it does fine till warm. PLEASE HELP IM OUTTA IDEAS?!!

[@ray5961]

I'm not super familiar with the 95 Tacoma setup. Check our AFM or MAF also. Try running a can of Berryman B12 fuel injector cleaner through the tank also. I'd also check your plugs or install brand new spark plugs - that can help a lot of times.

[@glenmaney-r6e]

I did change the plugs but same results. I however didn’t change wires or distributer cap yet.

[@glenmaney-r6e]

Thank you for your help , I will try Berryman b12

[@ray5961]

@@glenmaney-r6e some timor's that can really help

[@ray5961]

@@glenmaney-r6e Sometimes a new cap can help. It's always nice to have high quality spark plug wires. Does your motor have a AFM or MAF sensor? Sometimes disconnecting the negative lead of the battery or pulling the EFI fuse will help also, since it clears and resets the ECU and allows it to recalibrate its fuel trim stuff.

[@date6431]

I’ve been doing some fine tuning on mine going off of some of your data myself. Currently having a problem at cold start where I have no high idle. IAC is currently at 4.5 turns. I have replaced the coolant temp sensor on the right and in testing the one on the left “timer” it reads 0.00 ohm’s on my meter. So that sensor is bad, correct?

[@ray5961]

Yeah, that Timer switch on the left of the temp sensor should not be 0.00 ohms. The Toyota service manual shows that it should read 30-50 ohms when the temp is below 50 degrees F and 70-90 ohms when the temp is above 77 degrees F. They also specify that if you check resistance from the STA lead (which when looking directly into the sensor on the intake runner, it's the metal tab on the left when looking at it / right side of the vehicle) that to ground should read 30-90 ohms at all times (regardless of the temp). page FI-94 in the shop manual.

[@CNAEVR]

Man, I've had many similar issues, but the main one is that once I'm warmed up and coming to a stop, she simply cuts off completely. Thankfully I have a manual transmission, so I can just restart on the move - but still, quite annoying. 94 22RE ~285K.

[@ray5961]

Check to see if your AFM door is binding maybe? If that door doesn't return closed smoothly and rapidly, it will cause that issue. I have a recent video talking about it here kzbin.info/www/bejne/pXOlo2qDhdSLl9ksi=WU-hFqZ_4dv4nxXo

[@jacobreedmcdaniel6056]

Hi Ray, I've got a question for you. My 94 pickup with a 22re is idling very high at operating temperature. (I don't have a tachometer, but sounds like 2k rpm at least). Would you suggest turning my IAC clockwise or counterclockwise? Or should I look somewhere else for my problem?

[@ray5961]

I would check to see if the door inside the AFM is binding and sticking open. Also check to see if the coolant lines running to and from the IAC valve are warm to the touch - if either are cold, it can indicate that there is a blockage which is preventing coolant from flowing across the IAC body and preventing it from shutting down at temp. If you want to rule in or out the IAC system, a quick and easy test is by just taping closed the air inlet hole for the IAC valve using some duct tape or something (wrap the tape over the lip of the throttle body opening, so it doesn't end up getting sucked into the motor). If you check my channel, I have a couple videos which show exactly how the IAC valve stuff works and which hole, but if you are looking into your throttle body (after removing that rubber elbow thing), the larger hole at around 6 o'clock is the air inlet for the IAC stuff. Tape over it and see if your RPM's level out once the motor is warm. It won't wanna idle when cold, but if it does idle properly once the motor is up to temp, then that's a pretty good indication that coolant isn't flowing through the IAC body like it should (it's that hot coolant which causes the internal valve on the IAC to shut and block air flow; when you put duct tape over the hole, you are basically just doing the same thing manually).

[@jacobreedmcdaniel6056]

@@ray5961 you the man. I took my throttle body out and it is gunked up pretty bad. it was stuck slightly open. I'll clean that, then check my AFM while I'm at it.

[@ray5961]

@@jacobreedmcdaniel6056 Nice.. good deal. Yeah get yourself some B12 chemtool (carb cleaner) and go to town. All that EGR stuff really dirties up the intake system on the 22RE.

[@laceygaldamez3521]

Hey question we have two iac valves because we have a spare motor. I got the bright idea to look at our spare before removing the one on the motor. Now upon removing the valve and inspecting the spring we found what appears to be pieces of a gasket in there. Not sure if that’s normal but it’s definitely not built up carbon. The spring appears to be in good condition. Any idea what this may be from (the gasket stuff found in the spring?)?

[@ray5961]

It's probably something which broke off some place and got into the cooling system. On mine, when I first took it apart, I found a bunch of RTV sealant stuck in there from when the previous owner(s) did some random shit. Not uncommon.. just clean it out and put it all back together basically.