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So, you pushed the plunger while racing the engine and the ISC didn't retract?

@the gold2

 

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Did it appear fully retracted at the time and that is why it didn't retract?

Pre-1995 - DTC codes OBD1  >>

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Honestly I believe that it currently sits, and was sitting, at its 'normal standard' static resting place when engine is off. So, when I raced the engine, it started off at standard rest position and did not budge.

Later I will snap a photo of its static resting position with a caliper measurement.

I had a chance to go to a junk yard yesterday and saw three 4.9 engines with the ISC. I checked the to and fro free play and also eye balled the plunger length as it rested on the throttle cable assembly. (I did not pull and buy any because at their normal junk price of about $30 its not worth the gamble)

It all appeared to be the same 'throw length' as what I observe with my original installed ISC and my spare one.

I will snap a photo in a couple of days just for reference.

I need to check my fuses and probably later put a digital meter onto the harness to check for power....I dread pulling the harness connector.. Murphy's law!

 

Thanks

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OK attached are two pictures.

I measured both units. The inboard unit and the spare unit I have at hand. I used a mechanical caliper device.

 

So, both units measure the same for the following positions:

1.) Plunger length extended normally without any throttle cable assembly in the way. From plunger 'head' outermost surface to the front plane of the plastic ISC body it measures 1.93 inch.

2.)  when I depress the plunger with finger (engine off of course) , the free play allows it to retract a bit and measures 1.81 inch in length. So the plunger free play to and fro is 0.128 inch. This former value ,of course,  is also the plunger length measurement when the inboard ISC unit is at rest with the throttle cable assembly resting on the ISC plunger head.

 

Again both measured ISC units display  exactly the same measurements.

 

Based on this and based on what I eyeballed at the junkyard's 4.9 engines, It seems that the inboard ISC unit is not fully retracted as it sits with engine off.

 

Question: Is there a specific fuse that corresponds to the ISC unit? If so, where is it located? Engine bay? Under what name?

DSCN6193.JPG

DSCN6194.JPG

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In the photo above, the plunger shouldn't be touching when the engine is off, there should be a gap.  I am going to pull @OldCadTech into this. 

I need to get into the manual.   There is a way to go into the DIC to extend the retract the ISC manually via the diagnostics.

Does it appear that its not moving AT ALL?

@the gold2

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Make sure minimum air idle is around 525.

I'm thinking the ISC is not retracting all the way but a Tech2 would be needed to monitor the TPS and ISC input/outputs IIRC....


1. Turn ignition ON engine off.
2. Open the throttle plate and press the ISC motor plunger for a while until it retracts completely.
3. The throttle lever should rests against the minimum air screw on the throttle body.
4. Disconnect ISC motor at its connector.
5. Turn the ISC motor's plunger so that the gap between the plunger and the throttle lever is 0.030".
8. Turn ignition OFF and reconnect ISC motor.

Perform an idle learn;


PROCEDURE FOR RELEARNING TPS AND IDLE THROTTLE ANGLE OFFSETS AFTER A BATTERY DISCONNECT AND/OR CODE
E52/E052 ON 1990-1992 DE VILLES, FLEETWOODS, ELDORADOS, AND SEVILLES AND 1987-1992 ALLANTES EQUIPPED WITH
4.1/4.5/4.9 PFI ENGINE This bulletin has been revised to include new procedures and add a model year. 


These "learn" routines allow the vehicle to compensate for TP sensor adjustment and the loss of air flow due to throttle body deposits. TP sensor and idle
learn procedures are to be done when any of the following occur:

* Battery disconnected for service

* Battery replacement

* Code E052/E52

* Throttle body replacement

* TP sensor replacement

Vehicle Relearn Procedure:

Inspect the throttle linkage for any signs of binding or improper c/c linkage adjustment. Ensure that the accelerator pedal is free and clear.

1. Ensure that the min air rpm is set to 525:

2. Make sure that the outside air temperature reading is at least 50 F.

3. TP sensor learn:

NOTE: Do not touch the accelerator pedal or steering wheel during the TP sensor learn procedure.

Ignition on (engine not running)

Enter diagnostics

Turn ignition off

Wait a minimum of 20 seconds

Turn ignition on (engine not running)

Re-enter diagnostics

Turn ignition off

Wait a minimum of 20 seconds

Turn ignition on (engine not running)

Re-enter diagnostics

Turn ignition off

Wait a minimum of 20 seconds

4. Bring the vehicle up to operating temp.

On a 1990 C/E/K vehicle, run the engine continuously for 18 minutes.

On a 1991-1992 C/E/K vehicle, run the engine continuously for 13 minutes.

On a 1987-1992 Allante, run the engine continuously for 18 minutes.

If this procedure does not correct the problem, install a new ISC motor and repeat.

 

 

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Page 6E-8 of the shop maunual states E006 ISC Motor under PCM outputs.

PFI diagnosis 6E-A-69

for PCM code E030 (ISC rpm out of range) has one select E007 output cycling to cause ISC motor to extend and retract. Is this a typo error?

 

Apparently another method to electronically retract the ISC is on page 6E-C2-16 'TPS adjytment"

"go to PCM override ES03 (ISC motor). and press cooler button to retract ISC motor.

 

This next part is confusing.. it states " after the ISC is full retracted. verify that the throttle lver is resting on the minimum idle speed screw. (confusing because it appears to me that this idle speed screw is not visible from outside because it is set behind the throttle lever or inside the throttle bdy behind the throttle lever).

Although you are correct that "when the ISC is fully retracted, the ISC plunger should not be touching the throttle lever."

 

My picture of the inboard ISC shows the plunger touching the throttle lever because the ISC is at a rest position with engine off. Normally it seems that in this , non-fully retracted state, the plunger does rest on the throttle lever and in fact the ISC plunger's slight free play is depressed backward. That is what I saw with another 4.9 engines and in the diagram 4 page 6EC2-4.

 

So far I can't verify that the iSC plunger is retracting fully by electronic manipulation. I think I need another person to observe unless the ISC stays fully retracted after the PCM manipulation.

 

this reply just coincided with tech's comment that I have not read yet....

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Hello Old Cad tech, thanks for your advice.

I will try to follow up on that after I can try it out. My last response coincided with your typing up tour response.

 

One other historical fact, leading up to this fixed E030 code, the car would periodically 'sail' requiring me to relearn the idle.

In other words it appeared that the engine would lose its idle learn periodically somehow (not having disconnected the battery or anything of the sort).

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Hmm, the "sail"/ loss of idle learn would indicate the ECM is losing battery voltage.

Pull the ECM down and with engine at idle tap it with the palm of your hand, top and bottom, if you get a stall or a noticeable rough running replace the ECM.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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yes the E030 is "hard". Funny thing is that when I enter the diagnostics with engine off it reads E030 history. But with engine on, the check engine light goes on and the E030 is current. (The 'history e030 with engine off was not due to ignitin/engine on cycling with lack of high idle problem)

So, it being current wit engine on is what I mean by 'hard'.  NO E052 current but in history, probably due to battery disconnect recently.

By the way I normally had the trickle charger plugged into the cigarette lighter for battery maintenance since the car remains garaged alot. Could this have affected the PCM over several months?  Or if the trickle charger began to get defective in electronically monitoring full and trickle charge? To me it seem unlikely since the ignition is off always with the trickle charger installed.

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quick update: I tried holding the throttle lever wide open with key on(engine off) and tried to depress the ISC plunger. It would not budge. Twice.

I also just noticed a code in history that I may have recently overlooked. E026-shorted throttle switch.

About 5 days ago I ran the diagnostic tree for that E026 and it passed. At least it seemed to pass. That was one of the suggestions in the E033 tree.

So maybe that test caused the E026 code? But it remains in history and not current.

Only the E033 reads current after every start up and CELight.

 

Next I will try to 'palm' the PCM and see what gives.

Maybe even swap it out... but I am thinking that if the ISC is defective, that test may be indefinite.

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You are making progress!  Good for you.

Thanks @OldCadTech !!

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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BodybyFisher and OldCadtech, here is an interesting update with PROGRESS !

I undid the far end of the inboard ISC harness and plugged in the spare ISC using its spare harness.

I turned ignition on (engine off) and tried to depress the plunger. It would not budge- twice. ( 1. Turn ignition ON engine off.
2. Open the throttle plate and press the ISC motor plunger for a while until it retracts completely. )

However with the spare ISC still connected I turned the ignition off and heard a slap ,slap, slap noise (at first I thought they were electrical sparks) but it turned out to be the spare ISC 'ratcheting'. The spare ISC motor sounded smooth but it was slapping inside the gear section- no doubt- and the plunger was not moving.

Did this twice to confirm.

 

So I hooked up the inboard ISC with its own inboard harness and tried the same routine but got no motor noise or anything.

 

Process of elimination at this point tells me that the computer may be OK but I need to now remove the inboard ISC and swap harnesses and try again.

 

That may determine whether the inboard harness has a fault or ultimately whether the inboard ISC is kaput.

Preliminary question:  The new iSC offered up by rockauto and the likes, ac delco being more expensive, the pictures show no plunger. What is up with that? These things do not come with a plunger? Only one cheaper model ($54) had a picture with a plunger. Do I have to install the original plunger into a new replacement body???

 

Thanks !

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Minimum air MUST be set first !!! Completely remove the ISC and set the minimum air idle if you have to....

I'm a little confused about the term you used "inboard ISC". There is only one ISC. Where is this "far end"  connector located?

Try unplugging the ISC and pushing the plunger in, the purpose of this step is to retract the plunger so you can verify minimum air idle speed. If you push on the plunger and it does not move or doesn't retract all the way, replace the ISC. Throw away the ISC motor that ratchets also, I've never been able to save one that ratchets. 

The ECM could still be defective, don't by-pass the "TAP" test.

Look at the connector on the ISC and make sure the pins on the connector and the ISC are not damaged and the connection is clean and tight when plugged in. If the terminal lock is broken use a zip-tie to secure the connector so it can not move.

I've never dealt with an after-market ISC so I can't say how they are packaged but it is no big deal to unscrew the threaded portion.

In the top photo of the ISC a few posts back the plunger appears to be extended too far. When I refer to the plunger in those pics, I'm talking about the part the threaded piece goes into. There has to be a zero reference point, so push the plunger in and screw the contact piece in until there is a .030 gap between the throttle plate lever and the contact piece of the ISC. If there is still contact, the the ISC needs to be replaced.

Have you replaced a TPS recently?

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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12 hours ago, the gold2 said:

BodybyFisher and OldCadtech, here is an interesting update with PROGRESS !

I undid the far end of the inboard ISC harness and plugged in the spare ISC using its spare harness.

I turned ignition on (engine off) and tried to depress the plunger. It would not budge- twice. ( 1. Turn ignition ON engine off.
2. Open the throttle plate and press the ISC motor plunger for a while until it retracts completely. )

However with the spare ISC still connected I turned the ignition off and heard a slap ,slap, slap noise (at first I thought they were electrical sparks) but it turned out to be the spare ISC 'ratcheting'. The spare ISC motor sounded smooth but it was slapping inside the gear section- no doubt- and the plunger was not moving.

Did this twice to confirm.

 

So I hooked up the inboard ISC with its own inboard harness and tried the same routine but got no motor noise or anything.

 

Process of elimination at this point tells me that the computer may be OK but I need to now remove the inboard ISC and swap harnesses and try again.

 

That may determine whether the inboard harness has a fault or ultimately whether the inboard ISC is kaput.

Preliminary question:  The new iSC offered up by rockauto and the likes, ac delco being more expensive, the pictures show no plunger. What is up with that? These things do not come with a plunger? Only one cheaper model ($54) had a picture with a plunger. Do I have to install the original plunger into a new replacement body???

 

Thanks !

I think I mentioned above when I replaced it on a 95 Eldo last summer that the new ISC didn't come with a the adjustment plunger.  Measure the old plunger length and count the turns as you unscrew it from the old USC motor.  The transfer to the new USC was easy.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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On Tue Sep 20 2016 at 9:30 AM, BodybyFisher said:

To complete this thread, I ordered a Standard Motor parts ISC from rockauto, installed it and the idle is perfect, no more fast idle, and coming to a stop and stop lights are uneventful.

The new ISC did not come with the adjustable plunger.  I used the plunger from the prior, making sure that the plunger was in the EXACT location by counting threads and measuring it with a gauge.   With the throttle body cleaning, the engine is no smooth and responsive.

@the gold2 here is my post from earlier in this thread regarding the plunger

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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8 hours ago, OldCadTech said:

Minimum air MUST be set first !!! Completely remove the ISC and set the minimum air idle if you have to....

I'm a little confused about the term you used "inboard ISC". There is only one ISC. Where is this "far end"  connector located?

Try unplugging the ISC and pushing the plunger in, the purpose of this step is to retract the plunger so you can verify minimum air idle speed. If you push on the plunger and it does not move or doesn't retract all the way, replace the ISC. Throw away the ISC motor that ratchets also, I've never been able to save one that ratchets. 

The ECM could still be defective, don't by-pass the "TAP" test.

Look at the connector on the ISC and make sure the pins on the connector and the ISC are not damaged and the connection is clean and tight when plugged in. If the terminal lock is broken use a zip-tie to secure the connector so it can not move.

I've never dealt with an after-market ISC so I can't say how they are packaged but it is no big deal to unscrew the threaded portion.

In the top photo of the ISC a few posts back the plunger appears to be extended too far. When I refer to the plunger in those pics, I'm talking about the part the threaded piece goes into. There has to be a zero reference point, so push the plunger in and screw the contact piece in until there is a .030 gap between the throttle plate lever and the contact piece of the ISC. If there is still contact, the the ISC needs to be replaced.

Have you replaced a TPS recently?

OldCadTech, OK I used the term "inboard ISC" to differentiate between the ISC that is currently installed in the car (original factory part) versus the uninstalled spare I have and have used as a test reference.

 

The "far end" connector is a term I used to refer to the 'jumper harness' plug end that is opposite to  the socket that plugs into ISC body).

 

"Try unplugging the ISC and pushing the plunger in, the purpose of this step is to retract the plunger so you can verify minimum air idle speed. If you push on the plunger and it does not move or doesn't retract all the way, replace the ISC. Throw away the ISC motor that ratchets also, I've never been able to save one that ratchets. "   answer: Both ISC units I am tinkering with DO NOT retract. 

 

I have not replaced the TPS yet. I have not gotten a diagnostic code for that. I do have two new spares however. TPS is original with only about 56K miles. I will perform the computer 'rap' test as you indicated. Thanks !

 

BodyByFisher: OK now I understand the mechanics of the ISC better. The 'pintel' appears to be the external  threaded male 'bolt' (contacting the throttle lever) that goes into the female plunger of the ISC.

Amazon has a unit. I wonder whether you can view it and comment on quality. The AC/Delco one does not seem to come with the 'pintel' as far as pictures show on JC Whitney and rockauto. Besides, I am not sure if its really worth the extra money since parts now a days are all foreign made...  Also I understand about swapping out the 'pintel' now.  Thanks

Walker Products 220-1004 Fuel Injection Idle Air Control Valve

https://www.amazon.com/Walker-Products-220-1004-Injection-Control/dp/B00T1BT3ZM

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@the gold2

I think you can get away with the Standard Products unit, the make a standard and economy model, it's on rockauto. I used the economy model and it worked fine, but if you are planning long term there standard quality had always done good

If you buy from there look for 5 percent discount on this site.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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The Walker ISC looks good. One thing I wanted to point out in that product photo is that the plunger and the pintle are fully retracted.

Thanks for the clarification on the test unit and wiring.

The reason I asked about the TPS is it needs a zero setting as well or it will give erroneous throttle position information to the ECM. So that brings us back to the minimum air idle setting.

As a dealership technician we had an advantage because we had access to an abundance of parts, BUT one thing always rang true - NEVER, test with used parts unless they are known "GOOD" units.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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The only thing WORSE is replacing with a new part, only to find out much later that the new part was defective.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Assuming a new part is good will drive you crazy as it is not considered the problem anymore.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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