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Thread: 7AFE high idle - intake geometry?

  1. #1
    Forum Member Grease Monkey
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    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)
    https://www.youtube.com/watch?v=fKlHVdlir3A
    I have also moved the thermostat housing to under the intake, like shown in this video.
    https://www.youtube.com/watch?v=vW2c...l=CeasarSallad

    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.
    Could

  2. #2
    Forum Member 1st year Apprentice
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    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
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    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
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    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

  5. #5
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    Default Re: 7AFE high idle - intake geometry?

    Didn't really hink of the injectors and kind of remember a bad seal so orderd new one and replace them. But didnt change the idle.
    Yeah, were some vaccum lines, but have put sealant and plugged all of them when i installed the intake.
    Mangage to do a smoke test on the intake since my last post and i can now quite sure say the the intake do not leak.
    fiddle with the throttlebody screws without any luck and tried calibrating them correctly. Also mesured the TPS and seems to be ok.
    Cant find any air adjustment screw though. i know my old 4afe intake had one hidden but this one seems to be without?

    The IAC is combined thermo and electrical yes!

    What i do notic which i think is my problem is my ECU coolant temp sensor. When the engine is hot i can unplugg the CTS without it effecting the idle at all? (dont know if it should or just put the ecu in open loop?)
    Sadly the coolant sensor location is close to impossible to mesure with voltmeter, and are about the same work as replaceing it. So orderd a new one and pray that it is the problem.

    Feels like i have really rules out anyting else ecept thermostate.
    Still weird since this didnt happen when the engine was in the doner car.

  6. #6
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 7AFE high idle - intake geometry?

    In no particular order...
    1. Any chance that the thermo side of the IAC is leaking internally/not closing when the engine gets up to temp ?
    2. Electric side of IAC moving freely and not getting held a little open by accumulated carbon ?
    3. Engine not got too much timing advance ? Have you tried adjusting the ignition timing with the engine running ?
    4. Throttle plate not sitting slightly open at idle ? Have you tried pressing down on the throttle arm to see if
    it can close a fraction more and drop the idle speed ?

    The engine coolant sensor is primarily responsible for adding extra fuel when the engine is cold. Idle speed is
    primarily set by controlling the amount of air bypassing the throttle plate. If you can access the ECU plug that
    has the ECT input you should be able to check the cold resistance without pulling the sensor. With the plug out
    of the ECU you can measure between THW and E2 (4AFE but 7AFE should be the same) and at 20degC the
    resistance should be around 2kOhms.



    Cheers... jondee86

  7. #7
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    Default Re: 7AFE high idle - intake geometry?

    haha the dog life..

    I had the IAC apart and it's all clean and moving freely. im sure the hot water is getting there as well but it's like the ECU is keeping it open.

    Notic the if i stand still for ages so the fan comes on bc it gets to hot around there the idle goes down a little bit. :S

    Timing advance is spot on 10 degrees, but i have thought about my coil setup if that can make the ecu confused in some way.

    Checked the throttle plate and it should not be it, really closes well and makes a big difference when i get it leaking by adjusting to much.

    I think that in these late 7afe/4afe the ecu also controls the IAC but yeah that right i should be able to measure on the ecu. haven't thought about that, thanks!

    But damn what a difference the 7afe is in character to the 4afe. Car pulls really hard now!

  8. #8
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 7AFE high idle - intake geometry?

    Regarding ignition timing, when you say spot on 10deg this is with the engine idling and without any diagnostic
    terminals shorted ? I don't know exactly how you have your ignition set up but if timing information is coming
    from the distributor base, then it is likely that there is a two-step process to set the timing. First put the engine
    into diagnostic mode and set the base timing to 10deg. Then remove the jumper wire and the ECU will add some
    further timing to give (typically) around 15deg advance at idle.

    The reason I suggest turning the distributor while the engine is running is that if the engine for some reason
    (mechanical or electrical) has more advance than specified, the idle speed will be increased. Turning the distributor
    is an old school method of setting the idle advance... turn until you get the highest smooth idle and clean engine
    response when jabbing the throttle, back off a fraction, secure the distributor, and then drop the idle speed back
    to specification by adjusting the idle air.

    Regarding the IAC, if there is a thermo valve and a electric valve, the idle will be controlled by the ECU adjusting
    the electric valve. The thermo valve is there to provide extra air for cold starts when the electric valve on its own
    may not have enough capacity to supply all the air required. Thermo valves are not precision instruments and
    will usually still leak a little idle air even when fully warmed up. One test would be to clamp off the air supply to the
    thermo valve and see if the electric valve can hold the idle correctly.

    On an older Toyota it would be unusual not to have some kind of idle air screw. If you check inside the front of
    the throttle body, how many holes are located in front of the throttle plate ? There will normally be one to let air
    into the thermo valve and a separate one for an idle air bypass. There may also be one for allowing the PCV
    fumes to return (via channels cast into the manifold) to discharge in front of the throttle plate.

    Cheers... jondee86

    PS: Is this yout throttle ?
    https://www.autopart3.com/products/9...14615728259121
    Last edited by jondee86; Today at 09:23 AM. Reason: PS

  9. #9
    Forum Member Grease Monkey
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    Default Re: 7AFE high idle - intake geometry?

    Yeah is sport on when i have it in diagnostic mode is what i ment, set it when engine was running but due to the high idle i might be a little bit of maybe?! what i have heard the FE engines are quite kinky when it comes to not having the timing at 10 degrees. Engine runs really good tough if we take away the idle problem, no misfires and good power.

    hmm ok. im not quite sure what you mean clamping the air supply to the thermo valve? what i can see there is only one air intake to the valve and is at the front of the throttle body? so what do you mean?


    No my intake dont look like that, dont have the vaccum clock at least. mine look something like this:
    https://www.ebay.co.uk/itm/TOYOTA-AV...p2047675.l2557

    Only two hols before the throttleplate. One comes as you said from the PCV for fumes. And then it's one big towards the bottom for IAC.
    If i put my finger on the IAC port the engine dies straight away (and get a nice suckmark on my finger haha) so seems to be the only bypass

    But will check idle and mesure thermo sensor this weekend and see what i get!

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