How to adjust idle speed on '91 Eldorado 4,5l V8 ?
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HT4100 4.1, 4.5, 4.9 Discussion, How to adjust idle speed on '91 Eldorado 4,5l V8 ? in Cadillac Engine Technical Discussion; Hello, Excuse me for my approximative english, because i'am french... I have bought last week an 1991 Eldorado with 4,5l ...
  1. #1
    french-jeremy is offline Cadillac Owners Member
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    How to adjust idle speed on '91 Eldorado 4,5l V8 ?

    Hello,

    Excuse me for my approximative english, because i'am french...

    I have bought last week an 1991 Eldorado with 4,5l V8 Engine, it had 276000kms.
    It run very fine.

    Last week-end, i have wash the trottle plate, and now the idle speed is too high.

    When the tranny shift on the first gear before stopping the car, it made a stroke.

    How can i adjust the idle speed ?

    I have read the ODB codes :

    E026
    E052

    B111
    B552

    R022
    R024
    R026
    R033
    R034
    R061

    What are the seems of codes ?


    Thank you very much.

    Bye.

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    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: How to adjust idle speed on '91 Eldorado 4,5l V8 ?

    This is for 4.9 engine, but probably works on 4.5 as well
    Here is the ISC motor adjustment procedure for 4.9 liter engine outlined by the Guru. It should be the same for 94 Northstar. The gap is probably 0.060".



    "Hold the throttle lever open manually to get the RPM to about 2500 or so. Simultaneously depress the plunger on the idle speed control motor so that it starts retracting. Keep forcing the plunger to retract until it fully retracts and stops. Disconnect the wire connector to the idle speed control motor to "freeze" it.

    Return the throttle to the closed bore idle position. Use that torx screw that you have been jacking on to lower the idle to 450-500 RPM. 450 is the desired setting. The idle should come down to 450 and there should still be clearance to the ISC motor plunger. Nothing (like cruise control or throttle cable) should keep the throttle lever from going down to the 450 idle point.

    Idling at 450 with the ISC motor fully retracted turn the plunger until there is a .030 gap between the plunger and the throttle lever.

    Check the cruise link while at the 450 idle point. It should just be barely snug with a tiny bit of slack in the link. Make sure that there is a little slack when you adjust it. There MUST be some....just a little but some slack.

    Plug in the idle speed control motor connector and cycle the key off.

    Disconnect the battery negative cable for 60 seconds to erase any idle learn offsets that have been stored. Cycle the key on for 30 seconds and then off. Wait 60 seconds. Cycle the key again."

    If there is still no gap, unscrew the plunger and cut it or try the plunger from th eold motor. That's what I had to do with one of three ISC motors I installed on my 4.9 in ten years.

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    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
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    Re: How to adjust idle speed on '91 Eldorado 4,5l V8 ?

    Make sure you have the engine warmed to opp temp with the air cleaner installed before adjusting the ISC plunger.

  5. #4
    french-jeremy is offline Cadillac Owners Member
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    Thread Starter

    Re: How to adjust idle speed on '91 Eldorado 4,5l V8 ?

    Hello,



    I have changing my ISC motor, but i can't relearn the isc...



    With the plunger screw at the max, that don't touch the trottle lever, but the idle is at 1200rpm !



    There is a crank for push the trottle lever on contact with plunger.



    My Trottle body, or my Trottle body sensor is OUT ?



    Thank you.

  6. #5
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: How to adjust idle speed on '91 Eldorado 4,5l V8 ?

    Did you follow the procedure outlined in my previous post?

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