I just spent the weekend putting in a new water temp sensor and a used IAC (from cruiserparts). Once I got everything back together, the idle is way up to around 1800, and there it stays. I tested the new used IAC per the FSM prior to install and the valve seems to turn about 90 degrees for each prong grounded. Is this typical? I expected it would turn more. Further it appeared to be very open; I figured the ECU would just close it. Can anyone tell me if it is operating normal and what I should test next? Thank you!
IAC ? and High Idle (3FE FJ80)
- Thread starter rkuffel
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- #3
I had a high idle (1200 rpm) so I tested the IAC which was completely unresponsive. I also tested the water temp sensor, which was also not functioning. I believe it was stuck in a cold closed loop but bottom line was the idle was high and now it's really high. 
Do you think the new IAC is functioning properly? Probably can't tell without looking at it. I will see if I can close the butterfly valve.
Do you think the new IAC is functioning properly? Probably can't tell without looking at it. I will see if I can close the butterfly valve.- Thread starter
- #4
I checked the butterfly valve and it seems to be functioning properly. It opens and closes smoothly. It does seem like one would need to be pressing on the throttle to be idling that high. There is a bit of slack in the throttle cable when in idle position, is that normal? The dash pot seems to be operating normally but I do wonder if the bolt that hits the dash pot should be backed off. I'm also going to try and pinch off the air going into the IAC and see if that makes a difference...ugh.
The ISC and the TPS work together. If the ISC is known to be good, then check the TPS according to the FSM.
If the TPS is giving the ECU incorrect information, the ISC will be set wrong by the ECU.
If the TPS is giving the ECU incorrect information, the ISC will be set wrong by the ECU.
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- #6
I will give that a look too; thanks for the reply. I will post my findings...
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- #7
First, thanks for all the help, i am losing my mind with this thing.
Tonight, I manually closed the IAC valve (using the battery) and when I started the LC, the revs were down around 900 in neutral and 650 in gear (from 1800 rpm previously). As the LC warmed up the idle slowly crept up to about 1200 rpm. I drove around the block and the idle keeps creeping up, to the point where if I let off the brake it wants to accelerate. Yikes! I have not checked the TPS yet (I think I'm scared to see what I will find). Since I don't have another vehicle I think I will manually close the valve again and then unplug the IAC so the idle doesn't creep up. This will give me a chance to do more testing.
Tonight, I manually closed the IAC valve (using the battery) and when I started the LC, the revs were down around 900 in neutral and 650 in gear (from 1800 rpm previously). As the LC warmed up the idle slowly crept up to about 1200 rpm. I drove around the block and the idle keeps creeping up, to the point where if I let off the brake it wants to accelerate. Yikes! I have not checked the TPS yet (I think I'm scared to see what I will find). Since I don't have another vehicle I think I will manually close the valve again and then unplug the IAC so the idle doesn't creep up. This will give me a chance to do more testing.
oestlarsen
SILVER Star
Hm...You had high idle before and now again with diff iac. I monkeyd with and cleaned mine a while ago and recall 3 things..
1. I saw no diff when unplugging it short term
2. The fsm said it must bark twice after turning motor off...mine does and you can hear it
3. After cleaning it ran erratically for a few cycles. Not sure how many times you have stopped and started motor..
Oh, i never really addressed my low idle and light stumble when hot :-(
1. I saw no diff when unplugging it short term
2. The fsm said it must bark twice after turning motor off...mine does and you can hear it
3. After cleaning it ran erratically for a few cycles. Not sure how many times you have stopped and started motor..
Oh, i never really addressed my low idle and light stumble when hot :-(
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- #9
If you are interested, here are the results of my TPS test:
Test 1 (0mm, VTA - E2): .752 ohms = OK
Test 2 (.0303in, IDL - E2): .096 ohms = OK
Test 3 (.0429in, IDL - E2): .116 ohms = Not OK
Additional testing showed that at .053in clearance between the lever and stop screw the TPS went to infinity. Thus it appears that the set screw or TPS could be out of adjustment by .010 inches.
Test 4 (fully open, VC - E2): 4.8 ohms = OK
Is it possible that being .010" off on the stop screw or TPS rotation could be causing my problem. That would be nuts! Then again it does look like there is only .010" between continuity and no continuity. Can someone please shed some light on this?
Also, when I shut off the car, which does run smooth, I cannot hear the IAC unless I use a stethoscope. I only hear it once for about 1 second. I know the plunger is moving, I just don't know if it is moving correctly.
Test 1 (0mm, VTA - E2): .752 ohms = OK
Test 2 (.0303in, IDL - E2): .096 ohms = OK
Test 3 (.0429in, IDL - E2): .116 ohms = Not OK
Additional testing showed that at .053in clearance between the lever and stop screw the TPS went to infinity. Thus it appears that the set screw or TPS could be out of adjustment by .010 inches.
Test 4 (fully open, VC - E2): 4.8 ohms = OK
Is it possible that being .010" off on the stop screw or TPS rotation could be causing my problem. That would be nuts! Then again it does look like there is only .010" between continuity and no continuity. Can someone please shed some light on this?
Also, when I shut off the car, which does run smooth, I cannot hear the IAC unless I use a stethoscope. I only hear it once for about 1 second. I know the plunger is moving, I just don't know if it is moving correctly.
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- #10
Oestlarson, does your cruiser have the 3FE? If so, I think I will be sending back the IAC. I can't hear it operate without a stethoscope...
Thanks.
Thanks.
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- #11
Well I was able to get my old IAC valve apart and functioning again. It actually tests and acts exactly like the new (used) part, so I think the high idle is from something else. Next on the list, is to adjust the TPS to spec. Stay tuned...
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- #12
TPS is now within spec and it seems to have helped, however the idle is still hovering around 1000-1100. So, onto the next test(s): air conditioner switch and timing. To clarify, the 1000-1100 rpm idle is in neutral. When in drive it is around 700.
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- #13
Oops.
This is a interesting topic. I am having the same issues. I have a few questions below.
1. what is and where is the IAC?
2. what is ISC?
3. How did you get the TPS back in specs? what was your procedure?
1. what is and where is the IAC?
2. what is ISC?
3. How did you get the TPS back in specs? what was your procedure?
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- #15
When I said IAC and ISC, I was referring to the same part. IAC = idle air control (valve) and ISC = idle speed control (valve). Sorry if that was confusing.
The FSM describes the procedure for adjusting the TPS, it's also in the Chilton manual.
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- #17
Cool, that was next on my list. I will post my results...
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- #18
82 much, here is a great thread on how to test your TPS.
https://forum.ih8mud.com/80-series-...d-our-92-3fe-instructions-what-i-learned.html
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- #19
Does anyone know how to manually turn the engine at the crank? The retaining nut is huge and there isn't room for a socket.
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- #20
A wrench works...duh.
