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Thread: cold start 97

  1. #1
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    cold start 97

    My 97 has had cold start problems ever since I bought it last summer. I thought they would be easy to fix. HAHA!

    Toyota just replaced the engine with a JDM and it still has the problem. It will start, but you need to give it gas to keep it running. If you don't, it dies. Once it runs for 30-60 seconds its fine, and when warm it starts up again fine.

    They tried a different, used throttle body, which solved that problem but caused a dangerously high idle. That being an even worse problem, I told them to put the old one back in. They cleaned it all up, again, but the problem remains.

    This seems like it would be a cold start injector problem, but my 97 DX did not come with a cold start injector and is not wired for one. I'm stumped. They are stumped. I have an experienced tech working on it and he's stumped, unless we just need to get the right throttle body in there.

  2. #2
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    Re: cold start 97

    Here's what I think it might suggest - that you have two bad throttle bodies - there's an Idle Speed Control module attached to the throttle, controlled by the coolant temperature. Since the symptoms change with the throttle body - assuming the same ISC wasn't transplanted from one to the other - you've got two malfunctioning ISCs - one stuck closed on one throttle body and the other stuck open on the other.
    "If you find yourself holding a sledgehammer or a crowbar, it's time for a break."

  3. #3
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    Re: cold start 97

    I was curious so saw what appears to be a lot of relevant posts, one even about a '97 with high idle.

    Google
    toyotavantech.com: previa idle speed control valve
    "If you find yourself holding a sledgehammer or a crowbar, it's time for a break."

  4. #4
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    Re: cold start 97

    The tech who installed my JDM engine seems to have considered these other options and he seems to believe it is the throttle body itself that is the problem. I'm not sure what can go wrong in a throttle body itself.

    Now it has warmed up outside and it starts much better but last night it was idling high when I got home. I'll have to see if that impression continues. I will check it for the infamous black flakes but once again the tech assured me that he checked the coolant flow thoroughly.

  5. #5
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    Re: cold start 97

    Well, the Idle control valve is normally part of the throttle body - or I guess you could call it an assembly - so maybe there are some semantics at play, since I agree with you the body itself is a piece of metal with openings in it that are either clear or obstructed (and I count the throttle plate getting stuck sometimes on deposits as an obstruction). Not sure what you meant by coolant - it does circulate there to keep things toasty, but the valve is controlled by the ECU which reads engine speed and coolant temperature from sensors mounted elsewhere. If the motor or solenoid or whatever it is in the ICS isn't working or the moveable vane in the ICS connected to that is stuck or has limited motion, that sounds like your issue, assuming you've been swapping throttles each with their own ICS attached. The one that can't open internally to send extra air to the throttle acts like a stuck choke - starts well but will over-rev at idle. The other stuck open leans out the a/f mix too much at a cold start, and would matter less the warmer it was.
    "If you find yourself holding a sledgehammer or a crowbar, it's time for a break."

  6. #6
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    Re: cold start 97

    Sorry, ISC not ICS. Darn TLAs.
    "If you find yourself holding a sledgehammer or a crowbar, it's time for a break."

  7. #7
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    Re: cold start 97

    Not semantics at play if you mean my conversation with the tech. I grilled him to make sure he believed it was the throttle body itself and not the assembly. He responded with something about the tests he ran that went over my head, but was very firm that it was the body of the throttle body, so to speak. He's one of their most experienced techs and used to own a Previa until he sold it (to me, my first) about 23 years ago. Still, something is going on and people can be wrong but I tend to trust his ability to fix it over mine.

    My reference to the coolant was in regard to his response when I asked him about possible black flakes in the intake coolant pipes. He responded by saying he tested the coolant flow to the intake. I just went and cleaned the "T" where flakes collect and got a fair bit out, but I'm not sure that will change anything since clogging there is supposed to cause high idle when cold.

    The last couple of warm days it started perfect.
    Last edited by Previologist; 05-02-2021 at 06:48 PM.

  8. #8
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    Re: cold start 97

    What about using the throttle body which solved the cold start problem and swapping out the idle air valve with the one which didn't have the high idle problem. That seems like a logical step. Beware the people who are sure of something yet are unable to fix it. FWIW I have had 2 idle air valves go bad - it is not that uncommon.

  9. #9
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    Re: cold start 97

    The body that solved the cold start problem is the one and the same as the one with high idle. I sent it back.

    As for the tech who believes its the body itself and not the idle valve, I can only be sure that he knows a lot more than I do. It doesn't mean he's infallible.

    I'm taking it back to him tomorrow because now with warmer temps it isn't having the cold start problem anymore, but now this one is idling high too.

  10. #10
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    Re: cold start 97

    I've decided to be content with it as is. It doesn't idle dangerously high and the other morning when temps dropped into the 30s it started right up so I'll take it. If it starts causing problems at idle or startup then I'll revisit this.

  11. #11
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    Re: cold start 97

    It would be worth keeping an eye open for Previas coming into your local picknpull etc to get yourself a spare Idle Air Control Valve. It's worth having one. Plus, if there's a sensible opportunity (like when you next change the coolant, so that the IACV coolant passages won't drain when the valve is removed) you can put the scrap yard one in the vehicle to test it so you know if it's good or not while you have a functioning vehicle. Chances are a yard IACV will be good, but if you develop another idling problem later on and replace the IACV with the untested part and it doesn't fix it, you won't know whether its two defective IACVs or whether the problem lies elsewhere. Since it is foreseeable that you might have future idling problems a little extra hassle testing a spare IACV sometime in the medium term is good for peace of mind when dealing with the next idle trouble.

  12. #12
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    Re: cold start 97

    Just ran across a note I made referencing a video on this topic and thought of this thread. It's 1990's Camry-related (which is what I used it for) but probably applies to the Previa as well. It accounts for most of what I think I know about idle air control valves. So, for future reference:

    https://www.youtube.com/watch?v=WsP2-HKz7vE
    "#372 Better repair method Toyota Camry Idle Air Control Valve" (Zero Labs channel)
    "If you find yourself holding a sledgehammer or a crowbar, it's time for a break."

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