1987 DeVille Conv. 4.1 ICM still sets idle to high - Page 2
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HT4100 4.1, 4.5, 4.9 Discussion, 1987 DeVille Conv. 4.1 ICM still sets idle to high in Cadillac Engine Technical Discussion; Originally Posted by BigCadMan_1 I hate to chime in on this one but I had the same problem with a ...
  1. #16
    BigCadMan_1's Avatar
    BigCadMan_1 is offline Cadillac Owners Fanatic
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    Re: 1987 DeVille Conv. 4.1 ICM still sets idle to high

    Quote Originally Posted by BigCadMan_1 View Post
    I hate to chime in on this one but I had the same problem with a 1986 Sedan deVille. I work part time as a mechanic & the owner of the garage was a trouble shooter for Alfa-Romeo & a master mechanic for Audi. We have anywhere from 20 to 30 cars a week come through the shop & trust me when I say we see it all. Why am I telling you all this, because I had all the resources one would need to fix this problem & we could not. I replaced every part with-in the ignition to fuel diagnostic tree, replaced both ECM, BCM's & still zip! Paid GM 2 hours to trouble shoot & nothing but $200 bucks poorer! I traced every path from the fuse panels & was getting ready to do the same for all the relays but gave up! In the end we thought it might be a short somewhere in the wiring harness but like I said I gave up after 3 months and countless dollars. I disconnected the ISC (or else the car was unsafe to drive) sold the car as is & paid some back tax's.
    I have no advice for you, just this story. Take it as you like.
    BTW I'm sure carnut will chime in & give a good idea where to look next, I hope for all the best for you.
    Quote Originally Posted by cadillac_al View Post
    Hey bigcadman, did you try a new ISC on this adventure? And a new one still didn't fix it? That would be depressing.
    Yes, "I replaced every part with-in the ignition to fuel diagnostic tree" just to be clear here I'm not saying it can't be fixed, I'm just saying I could not fix it.

  2. #17
    fretless's Avatar
    fretless is offline Cadillac Owners Member
    Automobile(s): 1987 Cadillac DeVille Convertible
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    Re: 1987 DeVille Conv. 4.1 ISC still sets idle to high

    Success! Today I have replaced the ISC and did a little fine tuning. Everything works now. At the end it was the ISC no sensors BCM ECM etc.
    Thank you all for your input and help.

    Dan

    Cad_web_S.jpg

  3. #18
    cadillac_al is online now Cadillac Owners Connoisseur
    Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
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    Re: 1987 DeVille Conv. 4.1 ICM still sets idle to high

    Great news and the car looks great too!

  4. #19
    BigCadMan_1's Avatar
    BigCadMan_1 is offline Cadillac Owners Fanatic
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    Re: 1987 DeVille Conv. 4.1 ICM still sets idle to high

    GREAT! Good to hear you got it worked out, just in time for summer driving.

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