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SEFI 5.0 high idle characteristics?

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    SEFI 5.0 high idle characteristics?

    Hey guy's, been awhile. Hope all is well.

    I was wondering what the characteristics of the LOPO 5.0 engine's high idle is supposed to be like. I think my high idle is a little screwy but in all my online searches and reading my repair manuals I can't find the info I'm looking for.

    This is about my 1987 Lincoln TC. Still all stock under the hood. Haven't had any time this year to mess with anything other than repairs. Most of this year's driving season, I've noticed that the car will idle high for 25-30 seconds after starting. Is this normal? Most every other fi vehicle I drive (including my employers 10+ vehicle fleet) only idle high for 2-5 seconds after starting. Then they settle to an idle speed of maybe 200-300 rpm's above hot idle until they warm up. If they're started warm they settle to low idle right away.

    My car will run at what sounds like (no tach) 2000rpms for that 25 seconds. It does this when cold all the time and does it when it's up to temp about 75% of the time. Most of the time I find this inconvenient if I want to get moving right away. I won't shift into a gear until it's off that high idle.

    If this isn't normal behaviour what should I look at to get it back to normal? Other than this wierd little issue there's no problems with the car. No idle issues after it gets past the "start up procedure". Car runs good, gets pretty good mpg's for what it is. Heck, in my fleet of vehicles this is my economy car!
    1987 Lincoln Town Car Signature Series-102k miles- LOPO 302, AOD, open 3.27, Dual exhaust w/ Thrush Turbo mufflers

    #2
    high idle is dictated by the ECT IIRC. If the ECT is bad or not ever reading higher temps, idle will remain high for a longer time. If the TPS has a dead spot in it or the cruise control cable is adjusted a bit tight, you'll have issues as well. There's probably more things to check, but I can't think of anything else off the top of my head right now.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Originally posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Originally posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

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      #3
      As stated, won't hurt to change the ECT and TPS - as always, I suggest OEM if you can find them. They usually don't get changed often so why not? Cruise cable is possible but unlikely unless you fiddled with it or in the immediate area. Unless you have other symptoms, I doubt the ICM is faulty.
      What I Own: 1993 Mercury Grand Marquis GS
      What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

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        #4
        +1 ICM would cause other issues

        Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
        rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
        Originally posted by gadget73
        ... and it should all work like magic and unicorns and stuff.
        Originally posted by dmccaig
        Overhead, some poor bastards are flying in airplanes.

        Comment


          #5
          Have you checked for codes yet?

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            #6
            sounds a little excessive. My Mark VII is as close as I have to a stock speed density 5.0, and it's high idle on a cold start is about 1500 for 5 seconds then it drops down. The Towncar is similar but so much is changed on that I don't really use it as a basis. 2k is too much and 25 seconds is too long to hold it there. Probably not a sticky IAC if it idles down normally, problems there tend to cause a hunting idle as the little ball inside over-shoots where it should be. Bad temperature sensors could certainly do it though, that causes odd startup stuff.

            86 Lincoln Town Car (Galactica).
            5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

            91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

            1984 Lincoln Continental TurboDiesel - rolls coal

            Originally posted by phayzer5
            I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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              #7
              Yah, my '88 Will start up and run at something like 1,500 or 1,800 RPM from the sound of it. Holds that for about fifteen or twenty seconds and then comes down to 800 RPM or so. IAC could be sticky or perhaps the ECT is bad like others have mentioned. I'd just unplug the IAC to see how low it'll want to idle without it. If it idles so low it wants to stall, take the IAC off, take it apart, clean the snot out of it and lube up the stepper motor before putting it back together and throwing it back on the car. Then clean the throttle blade to ensure that isn't contributing to the issue. If it still idles high, replace the ECT and see what happens. Cleaning and lubing doesn't cost much, so I'd start there first.
              1985 LTD Crown Victoria - SOLD
              1988 Town Car Signature - Current Party Barge

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                #8
                20-30s is normal. If you read your owners manual, it even tells you to let the car run for at least a minute after a cold start before driving off with it.

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