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ISC not working; possible problem with relay
Topic Started: Jan 27 2015, 01:02 PM (5,934 Views)
freegeo
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Hanuman
Jan 30 2015, 03:52 AM
freegeo
Jan 30 2015, 02:44 AM
TripleThreat
Jan 30 2015, 02:16 AM
A) What if any testing have you done with the TPS? http://geometroforum.com/topic/1341780/1/ This is critical for the ISC to work right.

B) Have you considered trying different throttle body with an ISC? Correction, I saw you have changed the ISC, that may be part of the issue. I heard removing them from the TBI can damage them, maybe someone else can elaborate?

C) Has the ISC in your car ever worked right since you have owned it?

D) Have you changed the idle stop screw that comes from the factory with a black cap on it? (Which you should never do)

E) Have you ever pushed on the plunger trying to force the ISC to retract? This ruins them


I ask because it seems that most members here do not have ISC type TBI units here or at least they are not usually very vocal about it since I started on this forum when I bought mine. I have been down this road myself with my 94' because it has the "enhanced emissions" with the ISC and because it is not OBDII like yours, it is an even big PITA to diagnose!

I have done nothing to the tps. Just this week I put a whole throttle body With TPS and ISC on it. Didn't adjust anything.


c)I don't know I bought it and it didn't run right. Rebuilt the motor and this is what I have. No past history of the car.

d) Still has the black cap, no adjustments made.

E) not that i remember.

I did start it tonight after work and now it runs a t 1500 rpm and doesn't idle down once warmed up.
when engine is warm, are the small coolant lines to and from the throttle body nice and hot?

fast non pulsing idle on a warmed up engine while not rolling means the computer thinks the engine is cold, or the ISC has a problem internally.

everything from my previose post still would apply to this situation.
.........problem with ISC or wiring harness.
Small coolant lines (both of them) to throttle body get hot.
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TripleThreat


THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:06 PM.
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freegeo
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Metromightymouse
Jan 30 2015, 04:22 AM
TripleThreat
Jan 29 2015, 11:57 PM
I love this forum and no offense to anyone but I have noticed everyone loves to badger you about grounds if they don't know the answer. Don't get me wrong, having bad ground connections can create a whole lot of issues that can be difficult to reproduce and track down. But it's not the answer to everything.

This is why I have a few different throttle bodies that have ISC's on them as spares.
I doubt anyone will be offended, no worries. :thumb

Here is what happens;
Member X says he has some odd problem.
Experienced Member says to clean the grounds.
Member X doesn't respond and goes on talking about the issue and all the stuff he's tried. He's at a loss.
Experienced Member asks "did you clean your grounds?"
Member X says "I checked them, they're good and tight."
Experienced Member asks "yes, but did you clean them?"
Member X says "they haven't been touched, they are still tight so they should be fine, shouldn't they?"
Experienced Member takes aspirin for the headache from beating his head against the keyboard, then gets a new keyboard out of the stack he has ready for just this occasion and types "CLEAN YOUR &*#&((% GROUNDS". After backspacing he then types the whole spiel about grounds again and requests that he actually remove and clean them.
Mysteriously Member X then either never posts again or comes back singing the praises of how easy that was and they should have listened.

It ends up coming off as really insulting to someone who actually did clean the grounds, possibly even before starting the thread, but experience has dictated that if it isn't absolutely clear the grounds were removed, cleaned, and securely reattached, we better ask again.

Those of us that read a lot of threads are also guilty of not remembering something we read on page one yesterday when we are on page two today.

So, are you sure your grounds are clean and shiny and solidly attached? :P
YES MMM I am 1000% sure that I have removed the bolts from ground connections, Cleaned the connections and the grounding surface (ie intake manifold, fender, radiator support and distributor) and re tightened the connections at least twice. I even added a extra ground from the battery to the intake manifold. I'm pretty sure the ground are good.
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myredvert
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myredvert

Free, you're obviously doing a lot of probing and checking, but the question is, are you actually following the FSM diagnostic procedure (from the DTC for the ISC)? Several have asked if the ISC is actually functional, and you have reported that it doesn't idle down when warning up, but it may be time to stop randomly "checking" things and get down to the real business of logical and well developed diagnostics. I'm not sure you're actually using the FSM procedure because some issues should have been verified or eliminated by the time you get to backprobing and such.

From the FSM (this is for a 94, so verify with your FSM, but the very first check is a basic functional check to determine physical operation and to verify whether the problem is originating from the the idle up signal or the ISC/ECM themselves...

(ISC functional check)
Warm up engine to normal operating temperature.

• With engine running at idle, turn headlight switch to ON (observe ISC motor plunger). Plunger should move.

• Turn ignition switch to OFF.

• Let the engine cool down.

•Turn ignition switch to ON (observe ISC motor plunger). Plunger should move.


ISC motor did not operate in first test only

Refer to section 6E2-C1 (Chart C-1A) for electrical load idle-up signal diagnosis.


ISC Motor Did Not Operate in Either test

• Backprobe ISC motor relay with a test light from cavity H1H to ground.

Test light should light. Does it?

(the charts/tests then go on to logically determine where the problem is coming from)

If you want to verify your TPS is set correctly to eliminate that as a cause, avoid the thread and use the proper procedure from the FSM. While there is some good information in the thread (mostly the copies of the FSM procedures) the bulk of the posts include information that is not part of the correct FSM procedure, and in many cases is simply not correct.
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freegeo
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Hanuman
Jan 30 2015, 04:24 AM

the symptoms dont fit a TPS or throttle stop screw.
im not saying there isnt a underlying problem, but as of now the ISC just isnt funtioning right.
if you test it, dont adjust it unless you are 800% positive its out of adjustment!
the more potential problems, the harder it is to pin point the problem....personaly, i would get the isc functioning first, then check or adjust the tps.
The TPS has not been changed on the original one or the one I swapped out. The throttle stop screw has not been messed with and I will not do anything to it in the future.

I agree the ISC needs to be checked and make sure it is functioning properly. That is what I have been trying to do is check and see if the ISC is actually good or not. What is the proper way to check if it is working correctly.

I am looking for a procedure that you manually check it and see if the plunger goes in and out.
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freegeo
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Metromightymouse
Jan 30 2015, 04:31 AM


I am at least the partial source of that little tidbit and it's from personal experience. It isn't a problem to remove it, just don't leave it plugged in and turn the car on (been a while, but I thing starting it is where everything goes bad, but it's safer to just say not to turn the car on).
Yes the fsm states you can change them but to not plug the connector back in without it being attached to the throttle body. If you plug it in and it is not attached to the throttle body the plunger can extend out to far and damage the ISC.
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freegeo
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Metromightymouse
Jan 30 2015, 04:57 AM
To sum up what I understand of where you are;
(Assuming) The ISC has not been observed to move.
The throttle body with ISC has been swapped with an assumed working unit.
The individual wires have been checked and you have continuity between the ends.
The ECU was swapped and the car ran but no change to the ISC.

If that is all true... you are in the Twilight Zone...

Or, some part that wasn't tested is the issue or your test failed to reveal the part with the problem.

I'm assuming you back probed the connectors to check the wires. If so, pull the connectors off and confirm the individual wires are still fully inserted and locked into place. If they don't lock, when you plug the connector in it will just push it out. If all the wires of a connector check out then plug it in and pull it out a few times to clear the corrosion and make good contact again. While it's unplugged look at the end and make sure none of the female spades have broken off or that the curled ends that lock onto the male spade are opened up or broken off. Swap in a different relay.

If that doesn't reveal anything or clear the problem then I would recheck all the wires and make certain that they are not broken or shorted. Next I would confirm the ISC is capable of moving. You have looked at the schematic and know which wires run the motor in the ISC, use a 9v battery or a couple of jumper wires to the battery and briefly touch the terminals for the motor. It should move. Reverse the wires and it should move the other direction. Just be careful not to over extend the plunger. Quick touches should move it a small amount and you just want to make sure it's moving freely.
I'm in the twilight zone. You are correct in the summary.

The ISC has not been observed to move but i have not tested it manually.

The computer controls the ISC, what does the computer use to control it?

Input form TPS, Switch in the ISC?
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freegeo
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myredvert
Jan 30 2015, 11:43 AM
Free, you're obviously doing a lot of probing and checking, but the question is, are you actually following the FSM diagnostic procedure (from the DTC for the ISC)? Several have asked if the ISC is actually functional, and you have reported that it doesn't idle down when warning up, but it may be time to stop randomly "checking" things and get down to the real business of logical and well developed diagnostics. I'm not sure you're actually using the FSM procedure because some issues should have been verified or eliminated by the time you get to backprobing and such.

From the FSM (this is for a 94, so verify with your FSM, but the very first check is a basic functional check to determine physical operation and to verify whether the problem is originating from the the idle up signal or the ISC/ECM themselves...

(ISC functional check)
Warm up engine to normal operating temperature.

• With engine running at idle, turn headlight switch to ON (observe ISC motor plunger). Plunger should move.

• Turn ignition switch to OFF.

• Let the engine cool down.

•Turn ignition switch to ON (observe ISC motor plunger). Plunger should move.


ISC motor did not operate in first test only

Refer to section 6E2-C1 (Chart C-1A) for electrical load idle-up signal diagnosis.


ISC Motor Did Not Operate in Either test

• Backprobe ISC motor relay with a test light from cavity H1H to ground.

Test light should light. Does it?

(the charts/tests then go on to logically determine where the problem is coming from)

If you want to verify your TPS is set correctly to eliminate that as a cause, avoid the thread and use the proper procedure from the FSM. While there is some good information in the thread (mostly the copies of the FSM procedures) the bulk of the posts include information that is not part of the correct FSM procedure, and in many cases is simply not correct.
The 97 is different than the 94. Atleast the FSM is. I tested it per the fsm as much as I can. Part of it you need a dealer type scan tool to verify some readings.

I have not checked anything on the TPS yet but am going to see what the FSM shows how to check it.

I have the weekend off and plan on doing more testing.
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Metromightymouse
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Powdercoat Wizard

Here is a post with the pinout;
clarkdw
May 29 2014, 10:13 AM
Remove the connector and when you look at the ISC you will see 5 pins. Three in one row and two in the second row with no pin in the middle.
- - -
- . -

If you hook the nine volt battery up to the two on the bottom row of my little diagram it should go in or out depending on which polarity you hook it up as. In the FSM they call them pins 1 and 3.

Follow this link and go to page 6E2-A2-58. 94 ISC info


After mine got jacked up I wired it to a switch and a button and the battery. Flick the switch one way and push the button: Idle up. Flick the switch the other way and push the button: Idle down. Use it on the freeway: Cruise control. Take it to an oil change place: Noise Maker, Tech freaker. I'd forget to warn them and for some reason they always had to push the button. I'd hear the engine race and then they would come in and sheepishly say they couldn't get the engine to idle down. I'd have to go out and flick the switch and push the button. Happened 3 or 4 times at least.
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myredvert
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myredvert

Hard to believe the 97 FSM doesn't also first specify a functional check to point towards the idle up signal or the ISC itself, but if it doesn't, it doesn't.

Although, the functional check for the 94 is still be a good functional check that addresses both "paths."
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TripleThreat


THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:06 PM.
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Hanuman
"The Almighty Grounds Cleaner"

TripleThreat
Jan 30 2015, 05:41 PM
Why not just have an assistant operate the ignition to the on but not start with everything connected. Turn off the key and back on like they said above and watch to see if the plunger moves? This makes mine move...
no assistant needed, remove negative battery cable.
turn ignition to run....
then reconnect battery cable...

you will be standing right there as it moves.
:thumb
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Hanuman
"The Almighty Grounds Cleaner"

freegeo, I read some of what Mwebb wrote in the tps report. the ECM PCM needs input from closed throttle switch to activate idle circuitry AND to enable decel fuel cut off at Higher than 1200 rpm when throttle is closed IF the closed throttle switch does not function as designed there will be idle problems BUT more important - NO decel fuel cutoff
fuel economy will suffer [/quote
I do not have any decel fuel cutoff either
Jan 30 2015, 11:16 AM]
.........................................................................................
.........................................................................................

any one else catch this????

this little clue needed to be mentioned along time ago

if there is no hesitation while driving in lower gears at lower throttle position then the problem is with the TPS itself, not its adjustment.
hesitation would indicate its out of adjustment.

no idle contact would keep the isc from moving at all.

test the TPS and its wiring. it moved once allready because you had a fast idle that stayed when warm.....other times you have no idle speed control.

the lack of decelfuel cut off while coasting in gear means the ECM is not seeing the idle contact on the TPS.
YOU HAVE SWAPPED COMPLETE THROTTLE BODIES....SO TEST THE WIRING HArness itself. (sorry caps lock)

but while your there, test the ISC also......i would remove it, open it up and physicaly inpect then bench test it.


(quoting apears to be not working right today)
Edited by Hanuman, Jan 30 2015, 06:28 PM.
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Hanuman
"The Almighty Grounds Cleaner"

Hanuman
Jan 30 2015, 06:25 PM
freegeo, I read some of what Mwebb wrote in the tps report. the ECM PCM needs input from closed throttle switch to activate idle circuitry AND to enable decel fuel cut off at Higher than 1200 rpm when throttle is closed IF the closed throttle switch does not function as designed there will be idle problems BUT more important - NO decel fuel cutoff
fuel economy will suffer [/quote
I do not have any decel fuel cutoff either
Jan 30 2015, 11:16 AM]
.........................................................................................
.........................................................................................

any one else catch this????

this little clue needed to be mentioned along time ago

if there is no hesitation while driving in lower gears at lower throttle position then the problem is with the TPS itself, not its adjustment.
hesitation would indicate its out of adjustment.

no idle contact would keep the isc from moving at all.

test the TPS and its wiring. it moved once allready because you had a fast idle that stayed when warm.....other times you have no idle speed control.

the lack of decelfuel cut off while coasting in gear means the ECM is not seeing the idle contact on the TPS.
YOU HAVE SWAPPED COMPLETE THROTTLE BODIES....SO TEST THE WIRING HArness itself. (sorry caps lock)

but while your there, test the ISC also......i would remove it, open it up and physicaly inpect then bench test it.


(quoting apears to be not working right today)
start your geo and let it warm up.
put it in nuetral and start pushing it....
does the idle increase after a few feet? (push it at a decent pace.)
if it does increase the idle speed while car is rolling, is it a steady increased idle speed, or does it begin pulsing up and down?

this will test the idle contact, TPS position and wiring all in one shot.

no idle speed increase means no idle sigal is reaching the computer.
pulsing means TPS may be out of adjustment......but usualy this is just a little corrosion on a wire some where.
a increase in idle speed that remains steady means everything is right or very close.
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TripleThreat


THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:06 PM.
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