Faulty 1FZ-FE Idle Speed Control Valve / IAC (4 Viewers)

[ozarkmud]

Hi everyone,

This is an extension of my post for baselining our FZJ80: Baselining our first 80 series: A '93 '3x locked FZJ80 - https://forum.ih8mud.com/threads/baselining-our-first-80-series-a-93-3x-locked-fzj80.1301624/page-4

I was hoping to get more eyes on it.

I've been suffering from a low idle when warm, and it looks like the Idle Speed Control Valve is bad. Part number 22270-66010.

Granted, I took apart the valve before testing, but I can't see how I could put it back together so wrong that it wouldn't actuate. The resistance specs are good, but applying voltage according to FSM doesn't let the valve move in and out. It actually locks it in place, so it's nearly impossible to push in/out by hand.

All of the threads I've seen, I haven't found an actual documented case of this valve failing. So I'm wondering if I'm completely screwing something up, or if this does happen from time to time.

And if it's dead, what do I do? I can take the motor housing off and attach the valve to the throttle body and use it like an idle air screw, of course it wants to turn on its own. It sounds like it's a very expensive part. I'm wondering if I can jerry rig it for manual control, but preferably would fix the electronics.

Is this some kind of brushless motor, with some fancy electronics in the housing? I don't see how it'd work, otherwise.

It sounds like the earlier 1FZs have a different ISCV part number than the later years. Are they compatible?

Thanks!

Related threads:

* 96 fzj80 IAC valve - https://forum.ih8mud.com/threads/96-fzj80-iac-valve.1276462/
* Idle Air Control (IAC) testing - https://forum.ih8mud.com/threads/idle-air-control-iac-testing.707031/
* No More High Idle on Cold Start - https://forum.ih8mud.com/threads/no-more-high-idle-on-cold-start.891215/
* No high idle at start - https://forum.ih8mud.com/threads/no-high-idle-at-start.1293256/
* FZJ80 Idle Air Control Valve IAC 22270-66010 on EBAY fake or OEM? - https://forum.ih8mud.com/threads/fzj80-idle-air-control-valve-iac-22270-66010-on-ebay-fake-or-oem.1019584/

 

[ozarkmud]

Alright, I came up with a DIY manual fixed idle solution for now. I'd still like to replace the valve. Not sure if the newer part number works or not, but it looks like the same part. Maybe the presets are slightly different?

I took the motor shaft and put some rubber washers on both sides. On the side with the shaft to give it friction as it tightens in, and on the other side to set the depth. The depth was set by trial and error. It's a slightly high idle when warm and in neutral or park, and about 650 or 700 RPM when in gear. Not a bad compromise for the time being.

The rubber washers from a Harbor Freight kit, 67552. Mostly used the 8x14x4mm rubber washers.

I used electrical tape to seal the 3 holes, but silicone would be way better. Wasn't totally sure if this would work well enough, but so far it seems to.

I'm sure there's many better possible manual idle solutions, but this used what I already had pretty well. Will see how long it holds up, but hopefully I won't need it indefinitely.

 

[ozarkmud]

Has anyone used the newer ISCV (22270-66011) in place of the older ISCV (22270-66010) in a '93-94 truck?

My theory is that maybe it's configured differently to do a higher throttle setting to compensate for the lower first gear of the A343F transmission, but that it will bolt up. The newer ISCVs are easier to get. Either way, I'm not quite sure how best to get it. The manual fix is working for now, but a bit nervous about having my wife have to start it in the cold and do left foot braking.

I see '93-'95 listed as the years for 22270-66010 and '95-'97 listed for 22270-66011.

The '95 year overlap also matches this: 80 Series Newbie Guide - Slee Off Road - https://sleeoffroad.com/tech-zone/80-series-newbie-guide/

"Automatic transmission changes to the A343F. Some 95’s were produced with the A442F. The transmission type is printed on the label on the driver door."

If no one has done this, I'm open to being the guinea pig but would greatly appreciate it if someone has done it and is willing to share the results. Kind of a spendy part for a (relatively) simple task.

 

[jonheld]

The resistance specs are good, but applying voltage according to FSM doesn't let the valve move in and out. It actually locks it in place, so it's nearly impossible to push in/out by hand.

The ISC is a 4 coil stepper motor. If static voltage is applied to one coil it will lock in place. The only way to get it to move is to sequentially apply voltage to the various coils, and it will move in VERY small increments. The FSM explains this in detail.

 

[ozarkmud]

The ISC is a 4 coil stepper motor. If static voltage is applied to one coil it will lock in place. The only way to get it to move is to sequentially apply voltage to the various coils, and it will move in VERY small increments. The FSM explains this in detail.

It should still move back to one of those positions when voltage is applied to that pin, right? I was following the FSM for this, but maybe I missed something. I also did them in order and noticed no change at all.

 

[jonheld]

It should still move back to one of those positions when voltage is applied to that pin, right? I was following the FSM for this, but maybe I missed something. I also did them in order and noticed no change at all.

Again, the internal motor will not spin. It will move in 90 degree increments, assuming that you supply + and - to the correct terminals. When the motor rotates to the next pole, it will move the valve assembly in miniscule amounts. I can't stress miniscule enough.

 

[Malleus]

How did I miss this post? I would have bumped it, had I found it, instead of posting another.

 

[SNLC]

Has anyone used the newer ISCV (22270-66011) in place of the older ISCV (22270-66010) in a '93-94 truck?

My theory is that maybe it's configured differently to do a higher throttle setting to compensate for the lower first gear of the A343F transmission, but that it will bolt up. The newer ISCVs are easier to get. Either way, I'm not quite sure how best to get it. The manual fix is working for now, but a bit nervous about having my wife have to start it in the cold and do left foot braking.

I see '93-'95 listed as the years for 22270-66010 and '95-'97 listed for 22270-66011.

The '95 year overlap also matches this: 80 Series Newbie Guide - Slee Off Road - https://sleeoffroad.com/tech-zone/80-series-newbie-guide/

"Automatic transmission changes to the A343F. Some 95’s were produced with the A442F. The transmission type is printed on the label on the driver door."

If no one has done this, I'm open to being the guinea pig but would greatly appreciate it if someone has done it and is willing to share the results. Kind of a spendy part for a (relatively) simple task.

So we had a 93 that would dip rpms randomly while at stop lights/signs.

Tested the IAC and it tested fine. Put in a used one from a 95 and problem is gone.

Cheers

 

[Malleus]

Has anyone used the newer ISCV (22270-66011) in place of the older ISCV (22270-66010) in a '93-94 truck?

My theory is that maybe it's configured differently to do a higher throttle setting to compensate for the lower first gear of the A343F transmission, but that it will bolt up. The newer ISCVs are easier to get. Either way, I'm not quite sure how best to get it. The manual fix is working for now, but a bit nervous about having my wife have to start it in the cold and do left foot braking.

I see '93-'95 listed as the years for 22270-66010 and '95-'97 listed for 22270-66011.

The '95 year overlap also matches this: 80 Series Newbie Guide - Slee Off Road - https://sleeoffroad.com/tech-zone/80-series-newbie-guide/

"Automatic transmission changes to the A343F. Some 95’s were produced with the A442F. The transmission type is printed on the label on the driver door."

If no one has done this, I'm open to being the guinea pig but would greatly appreciate it if someone has done it and is willing to share the results. Kind of a spendy part for a (relatively) simple task.

Bump
@SNLC beat me to it!

 

[ozarkmud]

Thank you, everyone! I ordered a 22270-66011 to try out in lieu of my manual fix, which is still working surprisingly well.

 

[ozarkmud]

Turns out that the new IAC has the same issue. It does idle up properly when the A/C is turned on and idles high enough when cold. The old IAC may have been fine after all.

Does look like the 3FE has a manual air screw which I greatly appreciate for cases like this, though I could be mistaken.

Will have to figure out what other issue is causing this.

 

[Malleus]

Plugged bypass in the throttle body?

 

[ozarkmud]

Plugged bypass in the throttle body?

Could you elaborate on that more? I didn't know there was a bypass, nor where it is.

 

[Malleus]

 

[Malleus]

The IAC plugs the bypass when it's closed (when the throttle is open), and allows airflow into the bypass when it's open, allowing airflow at idle, when the throttle body valve is (mostly) closed. If this bypass is lugged with oil/carbon, etc., and the throttle body vale is closed at idle, the engine will stall.

 

[Malleus]

Could you elaborate on that more? I didn't know there was a bypass, nor where it is.

Does that answer your question? I'm pulling my son's TB tomorrow, hoping we'll find a clogged bypass that's killing the idle. If not, I'm swapping the IAC.

 

[ZackR]

Does that answer your question? I'm pulling my son's TB tomorrow, hoping we'll find a clogged bypass that's killing the idle. If not, I'm swapping the IAC.

I had a really low idle and was expecting to find a clogged bypass - but it wasn't.

I ended up pulling the IAC valve and running the FSM checks to confirm it was working. I "stepped" it all the way in and all the way out a few times to confirm.

After that I cleaned the passage for the IAC and the throttle body to make sure the throttle would close fully. I found that the throttle plate was not closing fully because one of the cables was too tight and the throttle body was dirty.

Finally I adjusted the TPS using a multimeter per the FSM. Once that was dialed in my idle went back to spec and it does the high idle at startup.

Here's a photo of the bypass for reference. I ended up cleaning up the throttle body and passages with isopropyl alcohol and an old toothbrush.

 

[ozarkmud]

Ah, that makes sense. I was thinking it might've been a different passage for some reason. Thank you!

 

[Malleus]

Update on the IAC (1994 vintage):

Background: low idle (150-300 rpm) after reaching operating temperature; idle 650 rpm when cold - no cold high idle. Recent problem (maybe three months); I've had the truck for about five years and it's run very well the entire time. Had to engage A/C to prevent engine stalling when stopped in gear (kept idle up).

Yesterday we removed and cleaned both the throttle body (which was dirty and oily, but much cleaner than I expected) and IAC valve. Bench tested the IAC. Passed continuity check, failed function test (no piston movement), although I could feel the motor clicking in my hand when the windings were energized.

Total time: about 35 minutes.

Since the IAC wasn't working, I figured I'd open it up and see what the post mortem indicated (I figured it was dead, so no photos. Sorry) After removing the three small retaining screws holding the stator (the black bell) onto the mounting flange, I pulled the stator free from the rotor. The rotor magnetism was very strong, and the two bearings spun freely. I unscrewed the plunger from the rotor and ran it up and down the screw length several times, to make certain it was freely moving up and down the shaft. I reset it all the way down on the screw.

The inner stator surface had a small amount of discoloration on it. I assumed it was contamination from somewhere, because there is a good amount (several tens of thousandths) of clearance between the rotor and inner stator surface, and the rotor surface looked undamaged. Unlike a brushed motor, there's nothing to wear inside. I lightly polished the stator surfaces with emery cloth and reassembled the IAC.

Total bench time, 5 minutes.

Retested both continuity and function, both passed. The FSM doesn't give an acceptable minimum movement distance for the IAC plunger, so I have no way of knowing if it's within spec or not. Mine moved a total of about 1-mm (approx; I didn't measured it).

Reinstalled everything.
Total time: 1.5 hours.
Pro tip: installation is the REVERSE of removal. Put the cables on the throttle body BEFORE mounting the throttle body onto the upper plenum.

Result: high cold idle, normal warm idle. Problem solved. For now.

Observations: I will say the plunger rubber bell, that is supposed to seal in the throttle body, didn't look new; I don't know how well it seals. I assume there's some blowby through the bypass when the throttle is open; I have no way to measure how much air is leaking past the throttle valve.

 

[ZackR]

Awesome - glad you were able to track down the issue!

The plunger on mine was not in perfect condition either but I don't think a tight seal really matters in this instance. I'm pretty sure the IAC does not close when you open the throttle, rather it stays where it was previously so that when you let off the throttle it doesn't have to scramble back into position to maintain idle.

If you haven't already it might be worth pulling the battery cable and letting the ECU reset now that it has a functional IAC to work with.