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Thread: what is this thing?

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    Default what is this thing?

    Hi all! I'm after a bit of knowledge from some of you that have experience with anything later than a holden red motor. ie engine management electronics.
    I have a 92 Pajero which idles at about 2000rpm. The idle adj is wound right back & I have traced the problem to sensor in the air filter assembly. I assume this is a air flow / oxygen /vacuum type sensor. Unplug it & the engine just about dies , plug it on & its up to 2000 rpm . Is this the problem or am I misleading myself . What is it & roughly what do they cost ?
    Things were SOoooo much easier before automotive electronics. - thanks



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    Junior Member circuit's Avatar
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    Mate that thing is the air flow meter, not likely to be your problem if its not working mixture goes out and probably won't idle at all.

    Check your coolant in the radiator , there is a idle up system which is turned down when the coolant warms up.
    Coolant could be low or hoses to throttle body blocked.

    Also look for intake air leaks, more common which will also cause high idle.
    There is also an idle speed control motor but when they fail , which is common the things have trouble idling not going up.


    Anyway look for intake air leaks and low coolant or blocked coolant hoses to throttle body.

    Circuit.

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    You may want to pop into the Pajero Club forum



    Leroy

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    Mitsbishis have a idle speed contol motor on the intake manifold, their known to fail, mine did on a 92 magna and exactly the same thing, it idled at 2000rpm.

    Luckly mine was manual so it didnt bother me till the next service.

    Common problem on Mitsus around that year.

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    thanks circuit - haven't checked the water hoses to the throttle body but they look to be in good condition & water level is ok. I don't think it is an air leak cause that would cause it to run lean & if anything it is too rich.

    God - is there an easy way to test the idle speed motor. Is it just a two wire device that I could check the voltage on as the engine warms up?

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    I havent looked into it watchdog as it was a company car, just took it in and got it taken care of.

    I did however change one for a fellow worker on his magna and it was just a plug with 2 screws holding it on.



    Edit i remember i got him one from pick a part in Broadmeadows for less than $40 second hand.

    It controls the engine speed by regulating the amount of oxygen going in.

    One thing i remember was checking to see if it clicked as the engine was turned on to see if it was working, but sorry mate its been a while since ive touched one, just working off what i remember mate.

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    Oh i just reread your original post where you wound your idle right back.

    Put it back to where it was.

    The throttle position sensor needs the throttle to be in a certain position, do not adjust your idle speed via the throttle stop like on old cars.

    The idle speed is adjusted via a brass screw fitted in the manifold, it regulates the amount of oxygen bleeding in past it.

    A little different to old school cars.

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    The first thing to check for here is a vacuum leak. Sometimes it can be difficult to track down broken hoses, but it takes a large vacuum leak to cause a high idle. Check the rubber hoses that connect directly to the intake manifold and throttle body. These are the most likely to fail. The best way to track down a mysterious leak is to remove a vacuum line and block its source with your finger. If the idle speed drops significantly below where it was before you removed the line, then you may have found your problem. Also look at the gaskets and air ducts between the throttle body and the intake manifold. It is unlikely, but you could have a leaking intake manifold gasket as well.

    The next thing to check is the throttle, check that the throttle is being completely released against the throttle stop by the throttle cable. If the cable is holding it open, make sure that the accelerator pedal is not caught on anything. Check that the throttle return springs are in tact. There are usually 2 springs around the base of the throttle arm and 2 pull-type springs between the throttle arm and the throttle body.

    The last thing to check is the Idle Control Valve, the idle control valve is a solenoid operated valve that lets air by-pass the closed (at idle) throttle plate, thus allowing the car to idle. Idle speed is adjusted by the computer opening and closing the valve. Make sure the valve has power and is not shorted, removed the valve and inspect for carbon build up as it is know to jam the solenoid. Removed the two phillips screws that attach the solenoid to the valve and spray the valve with carb/brake cleaner. Using an old tooth brush, scrub out the build up.

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    If you've you've upset that throttle stop screw then you have messed up the ecu....it has NFI about the throttle position and will probably hunt all over the place or go high...

    you need to go through the procedure of resetting that crew, usually until the valve just closes.

    touching that screw is a big mistake....


    I know...cause I did the same stupid thing...

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    Yes a good valid point by George, check all your vacuum hoses first.

    Sometimes i jump to conclusions.

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    Quote Originally Posted by Godzilla View Post
    Yes a good valid point by George, check all your vacuum hoses first.

    Sometimes i jump to conclusions.
    My brother thought it would be funny one day to remove the brake booster vacuum hose on my V8, start the car one morning at 5am to go to work, and BANG straight up to 3500rpm! Back then I was running 3in exhaust with only 1 muffler. Scared the shit out of me until I realised what he had done.

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    Quote Originally Posted by circuit View Post
    Also look for intake air leaks, more common which will also cause high idle.
    There is also an idle speed control motor but when they fail , which is common the things have trouble idling not going up.

    Anyway look for intake air leaks and low coolant or blocked coolant hoses to throttle body.
    Circuit.
    Just to repeat myself, most common cause of high idle speed will be intake air leak (vacuum leak).
    Check intake manifold gaskets, PCV valve , brake booster leak, hole in or split vacuum hose.
    Some of these also have a cruise control which has a pivot so the cruise can control the throttle cable, the pivot can get tight too.
    The idle speed motor can be check by measuring resistance between pins, there are 4 pins and 4 coils.
    You will be able to find tolerance on internet, otherwise I can look up tomorrow.
    I have replaced many of these though and all were because idle speed was too low or the car was stalling.
    If the throttle adjustment has been mucked around with it needs to be reset properly.
    Throttle adjustment (which adjusts throttle plate stop) is not the same as idle bypass adjustment screw which is usually on top of throttle body.

    Its not on gas is it, if that's the case then twice as many options to go wrong


    EDIT: if you want to check if the idle up system has coolant flow, feel the 2 small hoses going to throttle body from cooling system when engine is warmed up.
    Both should be hot indicating coolant flow at least.

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    Cool

    OK - Ihave checked for vacuum leaks as best I can. All vac hoses are in good condition.Accelorator & cruise control cables have zero tension on them at idle & the linkage is hitting on the stop screw. The water hoses to the throttle body are hot on inlet & warm on outlet so that may be a possibility, but the inlet did warm up quickly which it would not have done if there was a blockage. I don't know what the fuss is about the mechanical stop - it is only a mechanical stop and if its position was relevant it would show up by manually moving the throttle. The air bleed solenoid has me interested & warrants further investgation as a possibility. The idle bypass screw that was mentioned cannot be found, maybe it was on a later model. Thanks for all the leads & any other tips would be appreciated.

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    Save me trying to write it all LOL

    TPS (throttle position switch) is connected to the other side of your throttle shaft, when you readjusted the mechanical limit of your throttle you threw out the tps settings.
    Its just a large variable resistor (think volume control knob), the position of it varies the voltage passing through it to the ecu.
    The ecu uses the variable voltage readings to know the position of the throttle.

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    Problem fixed - Circuit wins the prize (a day with the screaming wife & kids). I ended up taking the outlet water hose off the throttle body, started the motor & sfa water came out. Then took the inlet off & plenty of water flow. Then I split the throttle body & took it off to check out. Attached garden hose to it & water flowed through OK. Took the stepper motor off & was greeted by a spring popping out & dissappearing into the garden (love these little surprises) Put it all back together & idles at 1200 when cold & you can watch it come down to 800 as it warms up. So I'm pretty sure it was a water blockage.
    Thanks to Godzilla for all his input.

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    Just do a throttle body coolant bypass, it's not really needed in Australia, mainly for colder/snow environments. Also adds extra heat to the air entering the throttle body which is a disadvantage.

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    Quote Originally Posted by watchdog View Post
    Problem fixed - Circuit wins the prize (a day with the screaming wife & kids). I ended up taking the outlet water hose off the throttle body, started the motor & sfa water came out. Then took the inlet off & plenty of water flow. Then I split the throttle body & took it off to check out. Attached garden hose to it & water flowed through OK.
    Glad to hear it worked out in the end.

    Quote Originally Posted by watchdog View Post
    Took the stepper motor off & was greeted by a spring popping out & dissappearing into the garden (love these little surprises) Put it all back together & idles at 1200 when cold & you can watch it come down to 800 as it warms up. So I'm pretty sure it was a water blockage.
    I'd say you were lucky to find the bits to put that back together, ive dropped the o'ring from the body before. Very hard to find once it disappears behind the motor.

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