Need Help On Two More Things
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HT4100 4.1, 4.5, 4.9 Discussion, Need Help On Two More Things in Cadillac Engine Technical Discussion; Hi all-- OK, so my car is pretty much running great (85 FWD Deville with the 4.1). I realized that ...
  1. #1
    awadecki is offline Cadillac Owners Enthusiast
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    Need Help On Two More Things

    Hi all--

    OK, so my car is pretty much running great (85 FWD Deville with the 4.1). I realized that what I thought was a timing mark was really paint that had chipped off, so now my timing is right on the money and the car is making good power (well, about as best as 125hp can).

    I do have one last question, though. My idle speed is very stable, but it is quite low (about 500 rpms). This isn't a problem at stop lights, but I have an issue if I jerk the steering wheel in one direction very fast--my car stalls out. It's fine if I keep a little pressure on the accelerator while doing this, but I'd like to fix it. I've performed the ECM switch test, and the P/S anticipator switch is working fine; if I turn the wheel fast in park, I can hear the idle speed up too.

    This also creates a problem when my A/C compressor cycles on/off even in Park, as my car dies right after the compressor decides to kick on, unless my foot is on the accelerator.

    I have my min. air screw set at about 500 rpms in Park, and my TPS sensor is reading properly (I believe). Any suggestions? What speed do your cars idle at in drive and park?

    Also, can anyone with an 85 Deville (85 only) take a picture of the vacuum hoses coming off of the brake booster? Just want to make sure mine are routed correctly.

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  3. #2
    Callidac der is offline Cadillac Owners Member
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    Re: Need Help On Two More Things

    Glad to hear that all is well with the timing

  4. #3
    awadecki is offline Cadillac Owners Enthusiast
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    Thread Starter

    Re: Need Help On Two More Things

    Anyone else have some ideas about the idle?

  5. #4
    NickySantoro is offline Cadillac Owners Fanatic
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    Re: Need Help On Two More Things

    Based on the commonality of symptoms, my first guess would be the connections at the idle air control valve or the IAC valve itself.

  6. #5
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Need Help On Two More Things

    Correct me if I'm wrong, but I don't believe there's an IAC on this car. Just the ISC motor. The ISC motor works, it moves in and out when turning the wheel, just not enough. The plunger can move much farther than it actually does, so it's not an issue with the length of it.

  7. #6
    NickySantoro is offline Cadillac Owners Fanatic
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    Re: Need Help On Two More Things

    Sorry, I had IAC on the brain, just having cleaned the one on our Camry.
    Is the ISC adjusted correctly? With it is fully retracted you should have about .030 clearance. The procedure to fully retract has been covered a few times. It's also possible the ISC motor itself has gone TU.

  8. #7
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Need Help On Two More Things

    I assume the 4.1 is just like my 4.9; it sounds like it needs the idle relearn procedure. You know, disconnect battery for a few minutes, reconnect and idle for 15 min or so then in drive 2 min, then with heat on 2 min. It's in the owners manual anyway.

  9. #8
    wmorrisw is offline Cadillac Owners Member
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    Re: Need Help On Two More Things

    Hope these pics help.
    If you need any parts let me know. Mine is being parted out. Everything works but cam went. Just did a tune up. Lot of new stuff, wires, starter and alternator to begin with.

    Woody
    wmorrisw2@comcast.net
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  10. #9
    peteski is offline Cadillac Owners Enthusiast
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    Re: Need Help On Two More Things

    The ISC should be able to fully adjust the idle speed by pressing the plunger against the throttle lever. On my 85 Eldorado there is no relearn procedure for ISC. Only adjustment is to adjust the minimum idle screw, then adjust the ISC plunger to stay clear from the throttle lever. Once those two thigns are done, the ECM should fully control the idle speed.

    You should go into the output cycling mode in the diag mode and see if the ISC cycles between full extension and retraction. When fully extended, the ISC should move the throttle lever by several degrees.

    Peteski

  11. #10
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Need Help On Two More Things

    It does...that's what is confusing. I'm going to reset everything today to factory specs (i.e. TPS and min air screw) and see if it helps.

  12. #11
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Need Help On Two More Things

    Hi all--

    The TPS was a bit off (it was reading 1 degree of throttle at min. air). I reset it to 0.5V at min air so that it would read 0. Idle is now perfect. If your idle is too slow on a car equipped with the Ht4100, perhaps this is your problem.

  13. #12
    Melrose is offline Cadillac Owners Fanatic
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    Re: Need Help On Two More Things

    Go to Advance Auto parts and spend two bucks for the code reader/timing set jumper tooll. Insert it in the ALDL connector witht the engine off, start the engine, and see if it says "set timing" on the Info Center. Time it and it will be right.

  14. #13
    Melrose is offline Cadillac Owners Fanatic
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    Re: Need Help On Two More Things

    LISLE makes the tool. It goes in the A&B slots in the ALDL. It will be the best money you've ever spent.

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