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Thread: 7AFE high idle - intake geometry?

  1. #1
    Forum Member Grease Monkey
    Join Date
    Dec 2018

    Default 7AFE high idle - intake geometry?

    Hello again! I once again have a kind of weird problem with my 7AFE engine that i putted rwd.

    It have a very high idle like when you startup during a cold day, but it run it all day(all the time). Doing quite some troubleshooting and cant narrow it down and would like som help to go further.
    what i have done is.
    -Open clean out IAC valve (made sure it moves freely) already looked nice.
    -Checked so it wont stuck air in the coolant side of IAC, i also can feel the intake getting hot so it coming water to the IAC.
    -checken timing and it's running spot on 10 degree when car is warm.
    -Used some cans of starter fluid to try to find a air leak, got non and plugged in a bad (unsure how accurate it is) vaccum meter and that showed 29 psi of vaccum.
    Also tried with compressed air into the intake to listen to leaks, no success.
    -Checked the MAP voltage and tried to add vacuum manually which made the motor run differently, so I'm guessing it works.
    -Checked all vaccum hoses and connection by blocking them of or moving it around and didnt do a difference.
    -Have run the car for a while so it's not the computer learning after it being reseted.
    -No misfires or anything like that.

    It seems to run a bit rich, might add to the high rpm?

    So the geometry of the intake is changed, so i have a 3D printed adapter which rotate the intake 180 deg, also a bend 3D printed adapter for the throttle body to make i clear the good.
    can be seen in this with the motor running. ( a lot of joint's so one would think it would be a intake leak)
    I have also moved the thermostat housing to under the intake, like shown in this video.

    So i had the car standing still for a good while running close to when the fan comes on the engine actually drop in RPM like it should but as soon as i start driving the car it goes back like it was.

    So i have orderd a new thermostat, ecu coolant sensor to eliminate that. But those worked in the car before the swap.

    Would changing position of MAP, FPR in the intake make a difference on what vacuum it sees and cause this problem?^
    Would the thermostat relocation might be the problem? The same method worked fine when i had it on my 4AFE-4AF.
    I also wonder if the COP's conversion can increase idle speed? since they react faster give a better spark they might be able to advance the timing more then the ECU is calculating?

    Any input would be lovely, need some input and ideas.

  2. #2
    Forum Member 1st year Apprentice
    Join Date
    Apr 2019

    Default Re: 7AFE high idle - intake geometry?

    The only way it can rev too high is if too much air is getting into the engine, so its either getting too much past the throttle plate because its not returning to its stop, or it got a leak somewhere you haven't found yet. Try starting the engine and blocking off the intake with a piece of card or wood. if still wants to run with it blocked off there is a leak.

  3. #3
    Forum Member Grease Monkey
    Join Date
    Dec 2018

    Default Re: 7AFE high idle - intake geometry?

    Yeah, though so too! But if i put my finger in the IAC valve opening the engine dies at once and cant hear any air getting passed.
    But this dosn't rule out small air leaks, but gone through the intake in very detail :S

    Check the throttle plate to and adjusted it on the loose side to rule it out.

    Hmm what i remember that i missed to check is if my breakbooster is leaking, will do it this afternoon.

  4. #4
    Junior Member Backyard Mechanic jondee86's Avatar
    Join Date
    Dec 2008
    Wellington, NZ

    Default Re: 7AFE high idle - intake geometry?

    I am not familiar with the 7AFE engine but I see what looks like a combined thermostatic and electrical
    idle-up valve that you have separated from under the throttle body. From the look of it I would guess
    that there originally were several minor hoses connected to that to provide a vacuum source for other
    systems like A/C idle-up, P/S idle-up etc.

    No doubt you have checked and blocked off any small hose connectors that suck in air while the engine
    is running. There are likely several more small hose connections on the throttle body itself for ancillaries
    and these also need to be checked and capped if they draw air in while the engine is running.

    If that is all secure then check that you are not missing a nose insulator off one of the injectors. A missing
    or damaged insulator (small rubber donut or 0-ring) will leak air into the intake manifold.

    And last but by no means least, there will be an idle air adjustment screw somewhere on the throttle body

    Cheers... jondee86

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