IAC Valve

[pmesfun]

Originally Posted by fenixus

I believe you broke something in the IACV motor mechanism? it might be not working correctly now... I am not too familiar with insides of IACV ...

Did you verify it can fully close and open? did you run FSM checks on it after repair? you might want to replace it if anything is not out of specs.

Did you verify the Throttle Plate stays fully closed at idle or it's open a little? it should be fully closed with engine idling in Park/Neutral.

Note that at engine shut off the throttle plate is supposed to be a little open (prevents freezing to TB walls in colder climates) thanks to functionality of Throttle Opener (vacuum operated).

IACV opens manually by hand, but not when the motor(black box) is on. The throttle plate stayed closed, but the was air coming out of the iacv, hissing sound. It was idling at 800 with the maf? and air box removed, also the hose going to the valve cover. The plate is slightly open like you said when the engine is off. When I put everything back I opened the iacv manually and put the motor back on. Now its idling at 1900rpm and the temp was at a 1/4 on the gauge. Motor isn't working?

[fenixus]

hmm, if it turns both ways manually it's a good sign. question is if the motor can open/close it when ECU commands it to.

IACV can be energized manually by jumpering terminals in its plug to battery, so I would try this.

on shut off car, unplug IACV electrical connector and attach 2 wires securely (e.g. using tiny alligator clips) to pins like in pic below. wires would need to be long enough to reach the battery posts, put alligator clips on other ends to.



borrowed from DIY by Mister Perkins:
5sfe IAC Removal (lots of pictures)

attach the wire to positive battery post securely, then attach the other wire to negative battery post or some good ground nearby and listen what happens with IACV motor, it should do "something".

then I would try starting car (both IACV wires jumpered/connected to battery) and see where it idles (if it does at all) and then on running car disconnect the negative wire from battery post/terminal (one jumpering the IACV) and see where the idle speed lands.

if the idle speed difference is like 1,000rpm between energized IACV and de-energized then I think motor works fine.

Note that running car with unplugged IACV connector will throw a code (P0125 IIRC), so you will have to reset the ECU later when you are done with testing, .e.g. by pulling the 15A EFI fuse.

I hope it makes some sense LOL

now, my other worry would go towards your faulty ECT for EFI sensor

whatever test you do, make sure the car is warm already, otherwise your ECT cheater sensor will be fooling the ECU at cold temperatures.
also since ECT for EFI is proven guilty at cold starts, i would just go ahead and replace it first and worry about IAC later.

[pmesfun]

I will do all of this tomorrow, if not Friday. Had to run an errand and it was idling at 2100k in P when at full operating temperature. Something isn't right.

[LynchburgCSI]

For those searching in the future... related thread: Does this sound like a motor mount issue?

[JohnGD]

Did you use the DIY to clean the IAC. That was a good DIY.

Now the rotor should spin freely in the IAC right? And if you orient the rotor in approximately the correct position and bolt on the motor you should see the magnet force it to a fixed position. The springy feel is from the magnets.

So when you move it by hand does it return to the original position?

Originally Posted by pmesfun

I will do all of this tomorrow, if not Friday. Had to run an errand and it was idling at 2100k in P when at full operating temperature. Something isn't right.

[fenixus]

you may have 2 problems, one is ECT (bad at cold, seems lowest it says is 40C/104F), the other thing might be a sticky/faulty IACV?

I can imagine car would be able to idle at 2,100rpm at warm when IAC got stuck at full blast, meaning allowing as much air as it can into the engine, so raising the RPM (computer just adds more fuel to match up the ratio) ... or your ECT sensor is not cheating only when cold

ECT for EFI is a crucial sensor for the ECU to base its further calculations on. since it cannot be trusted anymore then the ECU is being unknowingly fooled by it maybe more often than we know.

I would really suggest starting with new OEM sensor and going from there.
I think I paid like $50 (shipped free) for this sensor from online dealers a year ago.

Not sure if 1mz-fe design requires draining some coolant (to drop level) before removing old one (it actually might as the rad cap is highest point in system I think), but on my 5s-fe it took me 5 mins to swap them and no need to drain any coolant (sensor is located on top of the cooling system).

[pmesfun]

Originally Posted by JohnGD

Did you use the DIY to clean the IAC. That was a good DIY.

Now the rotor should spin freely in the IAC right? And if you orient the rotor in approximately the correct position and bolt on the motor you should see the magnet force it to a fixed position. The springy feel is from the magnets.

So when you move it by hand does it return to the original position?

Its clean, and turns with no resistance. I don't think the motor is changing the position of the valve. That is why I opened it all the way, to see if the motor would adjust. It doesn't return to any position it just stays where it is. BTW the magnet is damaged, missing a piece.

Originally Posted by fenixus

you may have 2 problems, one is ECT (bad at cold, seems lowest it says is 40C/104F), the other thing might be a sticky/faulty IACV?

I can imagine car would be able to idle at 2,100rpm at warm when IAC got stuck at full blast, meaning allowing as much air as it can into the engine, so raising the RPM (computer just adds more fuel to match up the ratio) ... or your ECT sensor is not cheating only when cold

ECT for EFI is a crucial sensor for the ECU to base its further calculations on. since it cannot be trusted anymore then the ECU is being unknowingly fooled by it maybe more often than we know.

I would really suggest starting with new OEM sensor and going from there.
I think I paid like $50 (shipped free) for this sensor from online dealers a year ago.

Not sure if 1mz-fe design requires draining some coolant (to drop level) before removing old one (it actually might as the rad cap is highest point in system I think), but on my 5s-fe it took me 5 mins to swap them and no need to drain any coolant (sensor is located on top of the cooling system).

I will try to get the ECT sensor, 2 local dealers have it for $49 and the other $46, pick up an iacv valve from the junkyard also. I'm assuming all 1mz iacvs all the same?

[fenixus]

ok, good. replace those 2 things and you should be fine.

for 1mz-fe (checked 99 avy MCV10 and 02 solara MCV20 it is same) the iac valve assembly part number is 17300-20020 ($190 from toyotapartseast.com), double check with dealer anyways and get a new gasket for IAC too.

ECT for EFI is 89422-35010 ($48 from toyotapartseast.com)

[pmesfun]

After this still need to fix the ps pump, oring is on backorder for two weeks.. Hopefully this the end for some time.

[fenixus]

Originally Posted by pmesfun

After this still need to fix the ps pump, oring is on backorder for two weeks.. Hopefully this the end for some time.

keep us posted and good luck!

[Jason.MZW20]

Here's my 1MZ IAC valve:


It's duty cycle controlled, so if the solenoids went bad, it just won't work.

I bypassed the throttle body heater by looping the hose that comes from the by-pass outlet.

[pmesfun]

Originally Posted by Jason.MZW20

Here's my 1MZ IAC valve:

It's duty cycle controlled, so if the solenoids went bad, it just won't work.

I bypassed the throttle body heater by looping the hose that comes from the by-pass outlet.

How would the iacv work without the coolant hoses? Isn't that how the iacv adjusts idle along with the ECT sensor?

[pmesfun]

Drove 65 miles total to the junkyard, basically its in the ghetto.
Anyways after 2 hours in traffic, I got a IACV from a 95 or 96 Avalon. The only difference is that the motor is white instead of black. Should I swap the black motor over to the this iacv.

[fenixus]

i wouldn't bother with swapping motor, especially that yours is broken?

plug it in and check how it runs, then get that ECT sensor and it should be all right finally

[pmesfun]

Originally Posted by fenixus

i wouldn't bother with swapping motor, especially that yours is broken?

plug it in and check how it runs, then get that ECT sensor and it should be all right finally

I was soooo lucky, got there 5 minutes before closing. Took me 10 mins to get it out and 1hr to get home. I might install it today, if not tomorrow. Surprisingly the junked avalon has a new radiator, hoses and cap and a new air filter.