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KurtW85
07-25-2005, 01:25 AM
Is there anyway to check that it is working right. Car is not running so this: http://www.cygnusx1.net/supra/library/TSRM_MKII/fi/FI_060.html
Will not work :confused:

Ps prferably a test of the car it is off right now. :D

MkIISuperSupra
07-25-2005, 08:48 AM
Yes you can test the ISC valve. The proceedure is on page FI61. When you are at FI60 click on the next page button at the top of the screen and the test proceedure is at the top of page FI61.

HTH
Leslie

Dave A.
07-25-2005, 11:58 AM
One quick way to test the ISC valve with it still installed is to see if it clicks several times when you switch off the ignition. If the stepper motor doesn't click then something is either wrong with the valve or the circuitry that operates it.

KurtW85
07-25-2005, 06:09 PM
Thanks Probable should have looked around a little more befor I asked. Anyone know any prices of one. new/used ranges of prices.
THANKS

pdupler
07-25-2005, 06:44 PM
OK, I've made that $325 mistake before so let me clue you in that the procedure in the TSRM is not real clear. It shows to hook up a battery and make contact with each of the pins in sequence and you should see the isc valve move. What it doesn't tell you is that one full sequence 1-2-3-4-1 is just one tiny step out of 125 steps. If you do it just once or only a couple of times, it seems that it barely moves and so you assume that the ISCV is bad. Not necessarily. Basically, you should do that sequence in the book 125 times, then the ISCV should fully extend. If you do the reverse sequence 125 times, then it should fully retract.

KurtW85
07-25-2005, 09:43 PM
Instead of doing all that what about the resistance check, what does that show? If the resistance is good is the iscv good or does it not show anything???
THANKS

StanS
07-25-2005, 09:50 PM
Also your idle "adjustment" screw should be set fully CW minus a 1/4-1/2 turn.

AlanG
07-27-2005, 08:34 AM
"Also your idle "adjustment" screw should be set fully CW minus a 1/4-1/2 turn."

What happens when this screw is tight (fully seated) and not backed off? My 7mgte was runnning like this in order to adjust the idle down. A few days ago from one run to the next the idle jumped to 12-1500 rpm. This suggests that air from somewhere else is passing to the intake and keeping the idle up. Where could it be coming from?

AlanG

StanS
07-27-2005, 02:19 PM
HoppyJim (Chief Toy mechanic trainer for 20 years for 1/2 of Canada) from Cressida site said to seat it (fully CW). I added the partial turn backoff (which is prolly not neccessary) cause my idle seemed faster by ear when I backed it off. Ear's not too reliable so rigorously correct (max iscv control range) is seated. The idle should always be 650rpm so u have to be bypassing the iscv (as u said). Maybe a tb vac hose is being leaked into or fed air by what the hose is connected to. Maybe the iscv gasket is leaking.

Your air temp sensor could be heating at idle if u have cold air in and if the jump to 1200rpm recovers to 650rpm in about 15 seconds or so. The cold air cools the AFM body in which the air temp sensor is mounted and the rpm runs high until the body and sensor heat up due to underhood hi temp. Until i wrapped my afm (with cold air in) I would idle at 900rpm when stopping and work down to 650rpm in 15-20 seconds. Wrapping the afm reduced the over idle speed to about 750-800rpm and reduced the recovery time to say 5-10 seconds.

AlanG
07-28-2005, 01:59 AM
BRIGHT IDEA? If the ISC valve is bad, does that mean that it is stuck in a fixed position? If its stuck in fixed idle up position, couldn't we use the test procedure to back it off to an unextended/closed position?

AlanG

KurtW85
07-31-2005, 12:58 AM
If it is dead it will not move while doing the prosidure. What about the click noise it makes while doing the prosidure, is that a good sign or bad? And it is fully retracted when it is sticking out about 1/4"? :confused:

AlanG
08-03-2005, 09:40 AM
If the ISC is not working due to electrical connections, I would think that the test procedure could move it to a closed position because you are directly applying the power.

Is there any manual method for altering the valve's position until it's replaced?

Anyone know what breaks on the ISC valve?

AlanG

StanS
08-03-2005, 09:56 PM
"Is there any manual method for altering the valve's position until it's replaced?"

Never heard of one.

AlanG
08-08-2005, 09:22 AM
From Hoppyjim:

From: "hoppyjim" <hoppy1@telus.net>
Subject: Re: Throttle body idle adj screw Correct Adjustment

On ALL Cressidas, Supras, etc., with an electronic idle speed control
(ISC) motor, the air passage adjusting screw in the throttle body must
be turned in fully clockwise, seating the screw and completely closing
off the air passage around the throttle plate.

This idle air passage and adjustment is used to set the idle speed on
engines that do NOT have an electronic idle speed control motor. It
serves no function on engines with an idle speed control, as it only
parallels the air passage regulated by the idle speed control (ISC).
The useless screw, and it's air passage around the throttle plate was
eventually deleted from later throttle bodies (it is not found on
7M-GE models), because it is redundant. If you back out the idle speed
adjusting screw in the throttle body on your Cressida with a computer
controlled idle speed, you will open the air passage, which will act
just like a throttle plate that sticks a little further open and lets
more air into the engine. If this screw is backed out, there will be a
parallel air path created around the throttle plate and the idle speed
controller.

If you back the screw out a little the computer may be able to
compensate for the additional air by closing the idle speed controller
down a little. However, if you back the screw out too far, and open
the air passage far enough the idle speed control (ISC) will be forced
close down completely in an attempt to adjust the idle speed, and
reduce it down to the target value. If you back out the screw even
further, the engine will then idle faster than the computer's
programmed idle speed, but the idle speed control will be unable to
reduce the idle speed further. If you stay within the idle speed
control's range of compensation, the system can usually overcome the
idle air leak you have created. However, you will have only succeeded
in forcing the computer controlled automatic idle speed control (ISC)
to drop a couple of notches further closed to compensate for the
additional air leak. Unfortunately, this compensation will only occur
when the engine has warmed up a little, and as long as the idle speed
control is functioning is in closed loop.

However, at start up when the idle speed control reverts to it's full
open (default) position, the car may be harder to start, as more air
will enter the engine leaning out the cold start injector's initial
squirt of fuel. At start up the engine will also initially idle much
faster wasting fuel, making the initial fan noise at start up even
more pronounced. The faster initial idle RPM at start up will also
increase engine wear as there is already an inherent lack of
lubrication on initial start up.

As well, the higher idle RPM at start up will increase shift shock
when "D" or "R" is engaged after initial start up. Even the "anti
squat" feature of the automatic transmission, which momentarily
engages second gear when the brake pedal is depressed, and the shifter
is moved from "N" to "D" may not be able to cope with the additional
cold engine RPM caused by the air leak in the throttle body. The
computer and the idle speed control will do it's best to conceal an
idle speed passage that has been caused to leak by inadvertently
unscrewing it, but the system can only do so much to remedy the
situation.

I have heard countless tales of how mechanics discovered this amazing
secret throttle body screw that the engineers apparently overlooked,
and all the magic it can do. Forget it! Any benefit is hogwash. On
cars with an ISC, turn the idle screw all the way in where it was
originally set at the factory, and leave it alone. If there is an idle
speed control screw on your Cressida's throttle body, be sure that it
is fully seated, then ignore it, as it serves no purpose.

With a warm engine, when the screw is initially backed out, the engine
will idle slightly faster, until the computer closes the idle speed
controller down to compensate for the increase in idle speed. When the
screw is initially turned inward, the engine will idle a little slower
until the computer responds and opens the idle speed controller to
compensate for the decrease in idle speed. There is a second or so of
computer response time delay to prevent the engine idle RPM from
aimlessly cycling up and down, hunting for the exact target idle
speed. Do not mistake this time delay, or lag in computer response
time for any real RPM change that turning the idle screw may have made
to hot idle speed.

The engine computer will control the idle speed. These engines are
very frustrating as they are so well engineered that there is no Holy
Grail of that little screw that only needs part of a turn to make your
car perform better. There is no mention in any repair manual of ever
tampering in any way with this screw. Don't mess with a good design.
Make it run as the engineers designed it to run, and it will run very
well indeed.

JIM HOPKINS

StanS
08-08-2005, 11:57 AM
Just reread HoppyJims ISC writeup that AlanG posted above and now I know why I thought the 1/4-1/2 turn opening was better, cause of the ecu built in delay. Think I'll seat mine now as HoppyJim reccomends.

AlanG
08-27-2005, 12:31 PM
Temp ISC fix - 7mgte
Recently, my ISC valve futzed and left it to idle at 1500rpm. Verrrrrrrrrrry expensive as my TPS is not set right and it yields only 15-16 MPG with some driveability adaptations. The TSRM has an electrical test for the ISC valve that triggers valve movement and a separate meter test reading.I didn't do the reading, but I did try the trigger test with the ISC on the car. The test calls for repetitive sequential grounding of the ISC contacts which should move the valve closed. (reverse sequence should open it). Well, I thought that doing the test could shut the valve and remain shut by leaving it unplugged. Tried it yesterday, but I just checked the TSRM and found that I didn't follow the proper sequence, so it didn't work. I may be able to try it again today.
Buuuuuuuuut, I did figure another way. I simply blocked off the ISC air intake line by covering the pipe with a double fold of aluminum tape and I opened the idle adjustment screw 2 turns. The pipe covering leaves no air for idling but opening the screw allows it to idle at 4-500rpm. This makes the car more driveable and hopefully more fuel efficient until I can get another ISC.
From the TSRM it looks like the 7mgte ISC might be the same as the 5mge ISC except for the wire plug. Would it bolt up? The 7m has a single plug but the 5m has split the connections into 2 plugs. Can anyone confirm?
What else didn't I think of?
AlanG

Dave A.
08-27-2005, 01:39 PM
The ISC valve rarely ever fails completely. Most of the time the pintle shaft just freezes up from carbon build-up. I would recommend that you remove the ISC valve and give it a good cleaning first to remove any carbon deposits and other crud. Then do the electrical test and see if the pintle valve moves freely like it should. Usually a good thorough cleaning is all that's needed.

Malibyte
08-27-2005, 02:10 PM
The ISC valve rarely ever fails completely. Most of the time the pintle shaft just freezes up from carbon build-up. I would recommend that you remove the ISC valve and give it a good cleaning first to remove any carbon deposits and other crud. Then do the electrical test and see if the pintle valve moves freely like it should. Usually a good thorough cleaning is all that's needed.


Mine no longer clicks after I shut off the ignition. I have a spare one here, just need to get around to swapping them. Just curious, though - if the above were the case (if it were just full of crud), would it click, or not?

Dave A.
08-27-2005, 04:16 PM
Mine no longer clicks after I shut off the ignition. I have a spare one here, just need to get around to swapping them. Just curious, though - if the above were the case (if it were just full of crud), would it click, or not?


No, because the click that you hear is the pintle shaft rotating/stepping to it's full open position. If the shaft is locked up with carbon deposits, you won't hear the usual click. Also, sometimes if the ISC valve locks up completely, the driver components in the ECU for the ISC valve can also become damaged. See if you can find an ISC valve that will pass the electrical test in the TSRM, then connect it to the engine harness w/o installing it on the intake manifold and see if it clicks when you switch off the ignition. If no clicks are heard, check the electrical connector and wire harness to verify that you have good connections to the ISC valve.

AlanG
08-28-2005, 02:26 PM
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Mine no longer clicks after I shut off the ignition. I have a spare one here, just need to get around to swapping them. Just curious, though - if the above were the case (if it were just full of crud), would it click, or not?


No, because the click that you hear is the pintle shaft rotating/stepping to it's full open position. If the shaft is locked up with carbon deposits, you won't hear the usual click. Also, sometimes if the ISC valve locks up completely, the driver components in the ECU for the ISC valve can also become damaged. See if you can find an ISC valve that will pass the electrical test in the TSRM, then connect it to the engine harness w/o installing it on the intake manifold and see if it clicks when you switch off the ignition. If no clicks are heard, check the electrical connector and wire harness to verify that you have good connections to the ISC valve.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks, Dave. Great idea to just hook up a loose ISC to the wires for testing. If high idle = open valve and I hear clicks when I do the short out procedure then it seems that the valve wants to move. Maybe it is jammed open and won't close any further?
I have hopes to get it off late this week for a cleaning and further test. If its bad, I will need another one.

celicasupravvti
08-28-2005, 09:07 PM
Hey Alan.. I'm asumming you have a 7mgte in your Ma61? If so... did it ever clicks (engine running and ignition off)after you do the swap or only recently it started not to click after ignition turn off?

AlanG
08-29-2005, 01:29 AM
Yes I have 7mgte in my 85 mk2. No I don't recall ever specifically hearing a click on shutdown.
Also, under this temp setup, it is really responsive off idle like it never was before.

celicasupravvti
08-29-2005, 03:20 AM
Ok then most likely it could just be the wiring and assuming that it never clicks since the swap. example: "7mgte engine in mk3 clicks when shutting off, idles fine, etc... then swap engine into mk2 and hence... no more clicks when shutting engine off" (Bad isc valve?) No.. more than likely bad wiring...

Are you getting any power(12 volt) w/key on to the isc valve(the 2 middle pins b/r)? Where is the power source from.. to the isc valve? Tapping into the wrong power source will cause a dead no ecu control isc valve operation. Even if you are getting 12 volt with key on.

The 2 wires of the isc valve black/red (b-r) is tap into the black/yellow(b-y) of the mk2's efi main relay power..both these wires(b-y)and(b-r mk3 engine harness) are found where the ecu compartment is. +B and +B1 is also tapped into the (b-y)of the mk2 efi main relay also. Be careful not to get the wrong wires.. (b-r) You can use a ohm meter.. probe the (b-r) at the isc valve connector and probe the other(b-r) in the ecu compartment.. using a Fluke 88 which has the alert beeping feature will greatly help. This is how my wiring is used. Others might be different but I know for sure this will get the isc valve working correctly if at all working. This wiring is directly simulating the stock wiring of both the mk2's/mk3's.

After you make sure all is connected correctly.. start the engine/turn off the engine quickly 3 -4 times.. Then on the fourth time.. you might have to give it some gas to keep it idling. The ecu will slowly learn.. let it idle for a few minutes.. and then hit the gas pedal a few times.. the idle should not drop or stall. Now turn off the engine and check for the clicking right after. I hope this help.. and not to confusing.

AlanG
12-28-2005, 07:25 PM
Got my ISC replaced with another used one and everything worked fine for 2 months .......until 2 days ago when I temporarily unplugged the wires when I was adjusting my TPS. Shortly after the warmed up idle speed in neutral has gone from 6-700 to about 1100. I am stumped as it can't be a clogged switch because it happened overnight (I am thinking).

AlanG

NashMan
01-02-2006, 10:06 PM
clean it

AlanG
01-03-2006, 02:30 AM
I reset the ECU by pulling the EFI fuse. When I turned the key, the dash lights came on and then all power went dead. I pulled and checked the EFI fuse and put it back in. Power was OK but I had to reset the clock and radio stations. Everything else seems fine including the ISC. Anybody got an idea why it went dead?

AlanG

Donn29
01-03-2006, 07:56 PM
I think that is a double post(its seems familiar)
also make sure the ISC plugs are in good shape. if you unplugged it then plug it back in and it suddenly doesnt work, that may be the prob.

Earl
06-21-2009, 01:03 AM
OK, I've made that $325 mistake before so let me clue you in that the procedure in the TSRM is not real clear. It shows to hook up a battery and make contact with each of the pins in sequence and you should see the isc valve move. What it doesn't tell you is that one full sequence 1-2-3-4-1 is just one tiny step out of 125 steps. If you do it just once or only a couple of times, it seems that it barely moves and so you assume that the ISCV is bad. Not necessarily. Basically, you should do that sequence in the book 125 times, then the ISCV should fully extend. If you do the reverse sequence 125 times, then it should fully retract.

Reviving a pretty old thread, but Phil's post (above) turned out to be just what I needed to hear. I was testing my factory original off my '85 and thought it was 'dead' (could just feel the ISC 'jiggle' in my hand each time I touched each of the four leads in sequence). So....I grabbed the one I have off an '84 from the local Pull-A-Part.....same thing. Hmmmmm.....somethings seems strange. Let me check cs.com and see what I can find.

That lead me to this thread and Phil's post specifically. Went back out and tested both and presto! Both of 'em were fine.

Phil, you are exactly right: while the TSRM is generally pretty good, they really dropped the ball on this test sequence by failing to mention the VERY minute movement that valve makes from just ONE pass of that sequence. I thought the valve would FULLY extend (or completely close) in just one full pass of touching the proper leads in sequence. Man, you can't hardly even tell the valve moves AT ALL from one single pass! The illustration shows either four successive 'arrows' inward or four successive 'arrows' outward (depending on the sequence in which you ground the four contacts), and with four leads to touch, one would pretty much assume that "one pass around and it is fully open; one pass back the other way and it is fully closed". Nope, not at all.

One thing I did find on my factory original valve and would like some feedback if anyone can help. I'm finishing up my 443,000 engine rebuild/engine bay restoration and I'm currently doing some final 'electro-mechanical' checks on a few items before I install them on the motor (hence the ISC valve test).

My factory original, which has already been cleaned thoroughly and the old gasket nicely scraped off did have one problem in the electrical check and that is it 'failed' part of the resistance check (page FI-61 in my '85 TSRM). Upon checking B1 against S1 or S3 (or B2 against S2 or S4) it would not register any ohms. However, if I reversed the test (B1 against S2 or S4.....B2 against S1 or S3), I would get an ohms reading in the low 20's, which is right in the middle range of where the TSRM says it should be (10--30 ohms).

I would like to use my 'original' (and it's already nicely cleaned and ready to install), and it the valve does work when I put it to the 'power on' test (thanks to Phil's test clarification). But, I don't really know what the ohms test really indicates and the fact that my original one does not pass that test as outlined in the TSRM. The one off the '84 DOES pass the ohms test and appears to be in nice shape, but it will need to be completely cleaned (it is not cleaned at all, though that '84 only had 72K on it and was in really nice shape before someone apparently wrapped it neatly around a tree or telephone pole).

Anybody have any idea what the ohms test REALLY shows and what it might mean if the ISC fails that test? Again, my original DOES seem to work fine with power applied.

Thanks in advance,

Earl