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ISC not working; possible problem with relay
Topic Started: Jan 27 2015, 01:02 PM (5,933 Views)
freegeo
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myredvert
Jan 30 2015, 01:59 PM
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."

It has those things in it but it is just laid out different. To be able to test something you have to look up 3 or4 different things to find wiring diagrams or which cavity in a connection is which. I doesn't look like link you sent me. I wish it was I would have figured this out already.
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freegeo
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Hanuman
Jan 30 2015, 06:53 PM
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.
I'll try this tomorrow. There is a big parking lot a block away and i can push it over there.
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freegeo
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I tested the ISC. Actually both of them. (original one on car) I went out and unplugged the connection at the ISC and hooked up an extra one I had(easier to see it move). Unhooked the negative cable and turned the ignition to run. Touched the negative cable to the post and nothing happens.

I used a couple of jumper wires to apply voltage to the ISC motor connections. The plunger moves in both directions. The plunger also works on the one on the car.

So everything checks out as far as the ISC is concerned.

Now to check the TPS and see what it is doing.
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Hanuman
"The Almighty Grounds Cleaner"

freegeo
Jan 31 2015, 12:53 PM
I tested the ISC. Actually both of them. (original one on car) I went out and unplugged the connection at the ISC and hooked up an extra one I had(easier to see it move). Unhooked the negative cable and turned the ignition to run. Touched the negative cable to the post and nothing happens.

I used a couple of jumper wires to apply voltage to the ISC motor connections. The plunger moves in both directions. The plunger also works on the one on the car.

So everything checks out as far as the ISC is concerned.

Now to check the TPS and see what it is doing.
TPS IDLE CONTACT or wiring in between.......thats all thats left.
one of the two is telling the computer not to "idle"
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freegeo
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I checked my TPS. I Have a reference voltage of 4.98 at the TPS. With a .014" feeler gauge between the throttle stop and the key on I had .75 volts. The plunger on the ISC was not touching the stop. I adjusted it to the FSM spec of .98 to 1.02. It was 1.00 after the adjustment.

It still doesn't idle up when cold and once warm it doesn't idle down. Stays around 1500 rpm. It is around 900 when engine is started and raises to 1500 as it warms up.

I didn't check the ground on the TPS but will before I try anything else.
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myredvert
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myredvert

Could the idle stop screw possibly have been (mis) adjusted to force the idle up previously by the PO or whomever when the engine was dying? That might go along with the TPS voltage being off. :dunno
Edited by myredvert, Jan 31 2015, 05:15 PM.
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freegeo
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myredvert
Jan 31 2015, 05:14 PM
Could the idle stop screw possibly have been (mis) adjusted to force the idle up previously by the PO or whomever when the engine was dying? That might go along with the TPS voltage being off. :dunno
Ding Ding Ding! We have a winner. :cheers

Yes when I put the other throttle body on it i didn't realize some one before me had changed the throttle stop screw. The cap was still on it so it was hard to tell it had been changed. That's why I could not get the idle down.
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myredvert
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myredvert

Quote:
 
Ding Ding Ding! We have a winner. :cheers
I just hope you realize the winner is you. It's not who comes up with the right answer, its important that the right answer is gotten to and you get your issue solved.

It was great to see how patient you stayed through the whole process and glad you were rewarded for it. :cheers
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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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I got it figured out but I still have some questions.


I checked the TPS voltage to the PCM per the FSM procedure. It states that the voltage should be between .98 volts to 1.02 volts. I was getting .75 volts. I adjusted it to 1.00 and it did not make a difference. I had to turn the TPS quite a bit to get it to read 1.00.
I could not get it to idle down past 1500 rpm. It ended up being some one had messed with the idle stop screw.

I checked the voltage reading on my 96 to see what it is. It was .64 volts. It runs correctly.

I put on my original throttle body since i knew it would idle down to 850 rpm's. I started it up and it ran at 850 rpm constantly. ISC would not idle up when cold just like before. I checked the voltage on the TPS and it was .75 volts. I adjusted the reading to .64 volts and it started to surge between idle and 2000 rpms.

I changed the TPS on it and set it to .64 volts. I start it up and it works correctly now. When driving it now goes to open loop when de accelerating like it should.

Looks like it is fixed but I am confused why the TPS signal setting is different than what is described in the FSM.

Posted Image

Does it matter where the DVOM is grounded? Does it need to be grounded to the battery or the ground on the TPS. I did it to the battery.
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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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TripleThreat
Jan 31 2015, 11:30 PM
I had considerable problems with this. Here is the deal, you have to block the throttle open 3.5mm = 0.14 not 0.014... That's the first thing.

Then take two sewing needles back probe 1&3 terminals on the TPS the one closest to the firewall being #1. Connect your dvm to these needles using alligator clipped jumper wires. Turn the ignition on but leave engine off now what voltage?
I just realized the same thing that I used a .014" instead of .140" Big difference there huh? :smackface I'll recheck it and see how close doing it the wrong way was. Has to be close or it wouldn't of helped it. I have T pins I can use to back probe it.
Hope someone else can learn from it too.
Edited by freegeo, Feb 1 2015, 12:43 AM.
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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
Feb 1 2015, 12:51 AM
In all fairness, the TPS report poster also puts 0.014" instead of 0.14" no offense to him because his post filled an obvious void but differences like that can make a HUGE difference...

I tried to tell you that the TPS and ISC are connected at the hip but no one was having any of it...

I have been down this road and had to play around with mine for several hours between .98 to 1.02 volts to get my ISC to respond correctly and do things it was designed to do like bump the idle for the A/C, headlights etc...

I am convinced that every TPS is set infividually based on a wide array of variables specific to a certain car... I wish there was a "one size fits all" voltage setting assuming the TPS is good, set and forget. that is just not how these cars are. They are quirky as hell.
They are quirky as hell.

.......................................
as i always say....
they are very electricaly sensitive.
the positive and grounding sides of the electrical system must be as clean and have the same resistance as it did when it left the factory....20 years ago. or the ECM will not function as designed. everything wil be electricaly will be out of spec.
notice most of the metro molesting is "compensating" for something electrical that the person couldnt get to work right.
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freegeo
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That is one thing I have realized after messing with this thing that if you make one little change it can effect 2 or 3 other things.

If you don't pay attention to eveything you will be :banghead !
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