ISC motor correct idling adjustment problem
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 8 of 8
Northstar Engines and System Technical Discussion Discussion, ISC motor correct idling adjustment problem in Cadillac Engine Technical Discussion; 94 eldo looked at all the post concerning ISC motor but can not get correct idle and car will push ...
  1. #1
    hardley-etc is offline Cadillac Owners Fanatic
    Automobile(s): 94 ETC 78 Eldo 69 Eldo
    Join Date
    Jul 2004
    Location
    PA
    Posts
    169

    ISC motor correct idling adjustment problem

    94 eldo

    looked at all the post concerning ISC motor but can not get correct idle and car will push

    installed new isc motor
    performed idle learn procedure
    performed idle speed control check from chart 6c-6
    no pcm codes present (code ps03 will be thrown if isc motor is slow or failed)
    select pcm output cycling p007
    does isc plunger retract and extend ---- yes
    start engine
    select pcm override ps03
    press cooler to retract isc plunger
    press off button and select pcm data pd11
    now my rpm is approx. 775 (is it absolutely critical to have exactly 700 rpm or lower?)
    book says above 700 rpm
    inspect for manifold leaks
    if no vacuum leaks replace throttle body
    below 700 rpm
    key off key on not running
    select pcm over ride ps03
    cooler to retract isc plunger
    press off button then select pcm data pd01
    wait 10 seconds record tps min value (mine 1.2)
    warmer extend isc plunger
    wait 10 seconds record tps max value (mine 8.3)
    subtract min from max
    below 10 deg --- adjust plunger out (did not adjust out anymore yet, logic seems like will make idle higher?)
    above 11 deg ---- adjust plunger in
    10-11 deg ok

    my plunger follows throttle lever to certain position and therefore car pushes (no gas pedal and car runs on its own)?
    there is no clearance between plunger and throttle lever at idle and if push throttle open with finger can see plunger extend too?
    but if adjust plunger in to try and get cleaance between plunger and throttle lever, the isc with ratchet and angle is above 11 deg according to pcm data pd01?
    any suggestions (what will ps13 learn and adapt reset do? pressing cooler button, will reset tps learn and idle learn values -- did not do this yet)

    currently car idles at 1000 rpm in park
    and approx 800 or 900 rpm in drive with foot on brake
    unhooked battery also to let reset
    linkage does not seem to be binding
    how does one check for proper tp sensor to throttle body installation?
    throttle spring seems ok

    can live with a little higher idle rpm but not the pushing of the car
    the powertrain OEM book is pretty precise but i don't get the ps03 code to perform additional tests (checking of circuity for opens or grounds), so will assume new motor is ok


    thanks in advance

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    9,577

    Re: ISC motor correct idling adjustment problem

    First, have you cleaned the throttle body bore so we are sure the throttle is not hanging on some carbon or buildup in the bore.?? Hold the throttle blade wide open with the air duct off and spray the throttle body bore with carb cleaner and scrub it with an old tooth brush. Wipe it out as clean as possible.

    Did you disconnect the cruise control link and see if the idle returns to normal.?? If the cruise link is too tight or was ever adjusted with the engine just turned off then it will be too tight. Take the cruise link loose from the throttle body and try it.

    Did you retract the throttle completely as I described and then freeze it by disconnecting the wires to the isc motor? If you do this, disconnect the cruise link and allow the throttle to return to the closed bore position the idle should be about 475-500 AND there should be some slight clearance between the plunger and the throttle lever. Need to know this.

    Performing the idle learn and such is pointless. It will not address your problem. Something is holding the throttle open...or there is a vacuum leak...that is why you need to retract the isc motor plunger, check for clearance at the plunger to the lever and check the idle speed to see what it is.

    The correct way to adjust the cruise link is to establish the throttle closed bore position with the engine idling at 475-500. THEN hook up the cruise control link so that there is just a slight slack in the link. If you hook it up without retracting the isc plunger first then it will not be adjusted correctly and will cause problems with the idle speed control.

  4. #3
    hardley-etc is offline Cadillac Owners Fanatic
    Automobile(s): 94 ETC 78 Eldo 69 Eldo
    Join Date
    Jul 2004
    Location
    PA
    Posts
    169
    Thread Starter

    Re: ISC motor correct idling adjustment problem

    update

    I don't be able to describe the situation too well I guess.

    Throttle body is clean. The ISC motor is new.
    I can not get a clearance between the isc plunger and the throttle lever unless I adjust plunger approx. 15 turns in, (but plunger will still follow throttle lever upon acceleration). Then the isc motor will ratchet at shut down and start up. When car is running and open throttle plate, I can not push plunger in with my finger and freeze it and disconnect the wires, it will only retract back to a position of idle of about 1000 rpm with force from my finger? Cruise control line is not holding throttle open, the conncetion wire has slack in it as you described. Throttle cable is not binding see below.

    Now If I do a PCM over ride PS03 the plunger will retract and there is a clearance and the idle will be correct. Throttle does not stick and is very responsive to snap closed to desired idle rpm and has a clearance. Ajusted plunger so TPS is 10-degree difference form min. angle to max. angel according to book.

    If car is shut off and started again rpm goes back to 1000rpm and the ISC plunger follows the throttle lever on acceleration. The PCM does not throw the code of PS03. The book says the TPS is an integral part of the ISC motor and can not be serviced.

    Exactly how does the ISC motor work. Upon a signal from the tps, plunger will retract when throttle is opened (acceleration) and when rpm's go below a certain level plunger extends to keep a certain rpm. My plunger follows the lever upon acceleration. Can the PCM not be signaling the TPS in normal mode? There is a check for this, but book says it is only necessary if a code of PS03 is shown. I can retract and extend plunger in diagnostic mode so I think PCM is able to control plunger. I have no PCM codes. When I do the PCM over ride, the plunger will retract and I get a clearance and things are okay (car idles fine, there is a clearance and car will not push down the road). I don't want to ride around in diagnostic mode with a over ride PS03 all the time. I am about ready to just disconnect the ISC motor.

  5. #4
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    9,577

    Re: ISC motor correct idling adjustment problem

    Quote Originally Posted by hardley-etc
    update
    When car is running and open throttle plate, I can not push plunger in with my finger and freeze it and disconnect the wires, it will only retract back to a position of idle of about 1000 rpm with force from my finger? .


    More later....but...per the above. Read the instructions carefully....


    Hold the throttle open with your hand so the idle is at 3000 RPM approx....

    WHILE HOLDING IT AT 3000............... with your OTHER hand press the plunger of the idle speed control motor. It will retract and keep retracting until it stops.

    With your third hand or have a helper remove the idle speed motor wiring connector at this point. (It really isn't that hard...spring the positive catch on the connector ahead of time, do the high idle with the throttle lever, retract the plunge by pressing on it until it stops moving and then yank the wire out of the ISC motor (WITHOUT RELEASING PRESSURE ON THE PLUNGER)

    Now you will have the ISC motor retracted and frozen. This has to work from what you've described.

    Release the throttle lever back to idle. There should be about .030 clearance between the throttle lever and the plunger AND the engine should be idling at 450-500. Screw the plunger in or out to get the clearance proper.

    Reread my previous instructions again....

  6. #5
    hardley-etc is offline Cadillac Owners Fanatic
    Automobile(s): 94 ETC 78 Eldo 69 Eldo
    Join Date
    Jul 2004
    Location
    PA
    Posts
    169
    Thread Starter

    Re: ISC motor correct idling adjustment problem

    thanks

    will give it a try this week end
    and report back

  7. #6
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    9,577

    Re: ISC motor correct idling adjustment problem

    Not knowing the history behind this car.....it is very very important to establish the proper idle speed baseline settings so as to see what is wrong. It is important to retract the idle speed control motor completely, disconnect it to freeze it and get the engine to idle at the required closed bore idle speed of 450-500 with the AC off. There is a set screw on the TPS side of the throttle body that is used at the factory to set the closed bore air rate..i.e...the 450-500 idle speed with the throttle blades closed. That may have been tampered with at some point....particularily if the vehicle was having idle speed or stalling problems and someone wanted to avoid replacing the idle speed control motor that was likely the problem all along. If you retract the idle speed control motor, disconnect the cruise control link, have clearance between the isc plunger and the throttle lever and the idle will still not come down to 450-500 then possibly you will have to adjust the set screw on the TPS side to get the idle down to the correct level. Once you figure what is required to get the idle speed down to 450-500 AC off with the throttle completely closed THEN you can adjust the plunger to have the necessary .030 clearance and reconnect the cruise link so that there is some slight slack. Finally, reconnect the isc wire connector so the PCM can control the idle speed.

  8. #7
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    50
    Posts
    9,577

    Re: ISC motor correct idling adjustment problem

    Quote Originally Posted by hardley-etc
    I can not get a clearance between the isc plunger and the throttle lever unless I adjust plunger approx. 15 turns in, (but plunger will still follow throttle lever upon acceleration). Then the isc motor will ratchet at shut down and start up. When car is running and open throttle plate, I can not push plunger in with my finger and freeze it and disconnect the wires

    Now If I do a PCM over ride PS03 the plunger will retract and there is a clearance and the idle will be correct. Throttle does not stick and is very responsive to snap closed to desired idle rpm and has a clearance. Ajusted plunger so TPS is 10-degree difference form min. angle to max. angel according to book.

    The book says the TPS is an integral part of the ISC motor and can not be serviced.

    Exactly how does the ISC motor work. Upon a signal from the tps, plunger will retract when throttle is opened (acceleration) and when rpm's go below a certain level plunger extends to keep a certain rpm. My plunger follows the lever upon acceleration. Can the PCM not be signaling the TPS in normal mode? There is a check for this, but book says it is only necessary if a code of PS03 is shown. I can retract and extend plunger in diagnostic mode so I think PCM is able to control plunger. I have no PCM codes. When I do the PCM over ride, the plunger will retract and I get a clearance and things are okay (car idles fine, there is a clearance and car will not push down the road). I don't want to ride around in diagnostic mode with a over ride PS03 all the time. I am about ready to just disconnect the ISC motor.
    No way should you need to turn the plunger that far.

    You have to open the throttle significantly so that it is holding the RPM high (like at 3000 or so) and then simultaneously depress the plunger to get the ISC motor to retract. It will not retract just pressing on it at idle.

    You freeze the ISC motor by disconnecting the wires. You don't "freeze it" and THEN disconnect the wires. If you are comfortably with the diagnostics and the overrides, then retract the idle speed control motor completely (instead of doing the open throttle/depress the plunger trick) and when it is completely retracted disconnect the wires to freeze it and check the RPM.

    The service manual does not go thru the 450-500 setup with the set screw because it assumes that no one is going to tamper with the set screw on that side...maybe that was a bad assumption in your case.

    When you say it retracts and the idle is "OK".....does that mean it is low enought to drive the car or that it is at 450-500...which is too low but a known setpoint that the system uses as reference. If the idle when there is clearance between the plunger is more than 450-500 then the wrong reference will be used and the system will be haywire.

    You are confusing the throttle position sensor (TPS) and the throttle position switch...usually called the closed throttle switch actually. The TPS is the device on the throttle body that is on the other side from the throttle lever that tells the PCM how far open the throttle is. It is NOT inside the ISC motor. The closed throttle/throttle position SWITCH is inside the ISC motor and is the "click" you feel when the plunger of the ISC motor is depressed when holding the throttle lever open.

    When the closed throttle switch is closed the PCM knows the thottle is resting against the ISC plunger and the PCM commands the correct idle speed by watching the engine RPM.

  9. #8
    hardley-etc is offline Cadillac Owners Fanatic
    Automobile(s): 94 ETC 78 Eldo 69 Eldo
    Join Date
    Jul 2004
    Location
    PA
    Posts
    169
    Thread Starter

    Re: ISC motor correct idling adjustment problem

    Another update

    I would like that thank you (bbob) for the precise written instruction given me. Over the weekend I got the 94-eldo northstar to idle at 900rpm in park and 700-800 in gear foot on brake and I got clearance between plunger and throttle lever. Car does not push any more. Sometimes I had to push the black piece of plastic (on the right side) attached to throttle body that the cable rest on closed a hair to get the 450-500 idle requested instead of the 700rpm that it was idling at, with plunger retracted all the way. I could not find anything that was actually holding it open this last bit. Maybe the spring is wearing a little? Cruise control was not the culprit. There is a small amount of carbon left where the plate actually pivots on the throttle body. I will clean this off good. Should this be the case or should plate close the last bit on its own to get the 450-500 or is the set screw out of wack? Don’t know how to describe it any better. I suspect someone had tampered with the set screw like you said. I have not actually found the set screw yet. I see the throttle position sensor and the plug. Is the screw near the sensor plug. The illustration in the OEM manual does not show the screw.

    On the weekend before I performed your written instructions but before, I went into the diagnostics and PS13 learn and adapt reset
    Book says PS13 may be used to reset the throttle position sensor learn and idle learn and/or garage shift adapt values. Pushing cooler button will reset throttle position sensor learn and idle learn values and cause “90” to be displayed. Note: power down cycle (key off for 30 seconds) must follow the throttle position sensor/idle learn reset in order for the learned throttle position values to reset. Each reset is allowed only once per ignition cycle.

    When I did the PS13 pushing cooler button the service engine soon light came on, code P080 is now current. I still do not know what the garage shift adapt is? Maybe someone (previous owner’s mechanic) with a scanner tool turned this PS13 off so the service engine soon light would stay off?

    Circuit description
    The diagnosis test checks to see if the initial throttle position sensor learn and idle learn values have been stored in the PCM. If these values have not been stored code P080 is set. Performing the TP sensor/idle learn procedure on the next page will cause P080 to become history.

    If code P080 does not change to history following the completion of the TP sensor/idle learn procedure this may be due top incorrect signals from the following sensors:
    Throttle position switch
    Throttle position sensor
    Vehicle speed sensor
    Transaxle range switch (park/neutral input)
    Power steering pressure switch
    Brake switch

    Now since I do not have any other codes coming up and the ISC motor is new I suspect the throttle position sensor is the culprit. I performed the learn procedure and also disconnected battery but the P080 is still current. So I will try to adjust set screw (once I find it) to get the 450-500rpm this week and see if code P080 becomes history. Maybe the precise baseline is not established yet.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting