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Thread: Erratic RPMs at idle/start-up | Solved with fuel system cleaner

  1. #11
    Moderator Eggman's Avatar
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    Quote Originally Posted by grevster View Post
    @Eggman, the oil cap was tight but i will leave a cardboard underneath to check for leaks overnight.
    Well, I meant something more like a leak in the PCV system.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.9 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 59.9 mpg (Imp)


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    Quote Originally Posted by Eggman View Post
    Well, I meant something more like a leak in the PCV system.
    The dealership said that they could not find any vacuum leaks, but they literally spent like 5 minutes on the car where they might have missed something.

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    Senior Member stevedmc's Avatar
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    Quote Originally Posted by grevster View Post
    The dealership said that they could not find any vacuum leaks, but they literally spent like 5 minutes on the car where they might have missed something.
    Five minutes is plenty of time to check for vacuum leaks on a cold engine. When I check for leaks I start the engine cold and spray carburetor in areas where I suspect a possible leak. If the engine idles higher when I spray a certain spot then Iíve found the source of the leak. Itís not rocket science and only takes a few minutes to perform this test.

    I donít think itís a vacuum leak though. It sounds more fuel related to me. I would do two Techron treatments (one after the other) and see if it fixes the problem. If it fixes the problem, switch to a top tier brand of gasoline and do a Techron treatment from time to time. I do a Techron treatment every time my tires are rotated and I try to only use top tier brands of fuel such as Shell and Exon.

  4. The Following 2 Users Say Thank You to stevedmc For This Useful Post:

    grevster (08-22-2019),Mark (08-22-2019)

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    Quote Originally Posted by stevedmc View Post
    Five minutes is plenty of time to check for vacuum leaks on a cold engine. When I check for leaks I start the engine cold and spray carburetor in areas where I suspect a possible leak. If the engine idles higher when I spray a certain spot then Iíve found the source of the leak. Itís not rocket science and only takes a few minutes to perform this test.

    I donít think itís a vacuum leak though. It sounds more fuel related to me. I would do two Techron treatments (one after the other) and see if it fixes the problem. If it fixes the problem, switch to a top tier brand of gasoline and do a Techron treatment from time to time. I do a Techron treatment every time my tires are rotated and I try to only use top tier brands of fuel such as Shell and Exon.
    I suggested doing this in post #6 of this thread, & I was about to say it again. I'm glad Steve said it instead, because it has worked for him.

    A rough idle after a cold start may be cause by your fuel injectors just being dirty. When cold, more fuel is required. Once the car warms up, less fuel is needed and the problem will go away.

    I would definitely give the Techron treatment a try! If I had your issue, it would be the first thing I would try at least.

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    grevster (08-22-2019),inuvik (08-22-2019)

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    Moderator inuvik's Avatar
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    Quote Originally Posted by Mark View Post
    I suggested doing this in post #6 of this thread, & I was about to say it again. I'm glad Steve said it instead, because it has worked for him.

    A rough idle after a cold start may be cause by your fuel injectors just being dirty. When cold, more fuel is required. Once the car warms up, less fuel is needed and the problem will go away.

    I would definitely give the Techron treatment a try! If I had your issue, it would be the first thing I would try at least.
    I agree, run a whole bottle of Techron in a tank to see if that cures the issue.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.4 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.5 mpg (Imp)


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    Mark (08-22-2019)

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    Senior Member stevedmc's Avatar
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    Quote Originally Posted by inuvik View Post
    I agree, run a whole bottle of Techron in a tank to see if that cures the issue.
    I do my treatments using half a tank of gas.

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    Quote Originally Posted by grevster View Post
    I am in Calgary and there is a dealership in NE here. It has 120k kms on it. Did the cvt fail prematurely? 130k kms should not be much regarding their life span, i am scared!
    .
    We've got a bunch of Mirage's down there too. Just towed back a wrecked one from Calgary on Tuesday. I've had to replace 3? cvt's so far and the dealer actually covered a 4th under warranty that was making noise.
    The first 2 cvt's had 300k and 220k kms. The one that made noise had around 60k. This latest one had 130k, it still drove fine but the fluid was black after changing it multiple times and I pulled it off the road when the driver mentioned it would stall when coming to a stop. https://mirageforum.com/forum/showth...-km-80k-miles)

    It's not common for them to blow up all the time. There is one common failure I found that's a cheap bearing that fails that takes out the entire transmission. https://mirageforum.com/forum/showth...inside-the-cvt
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    The engine still surges upon warm-up, but the vehicle otherwise has no problems. Now at 133,000 miles.

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    Quote Originally Posted by MrAmerica1776 View Post
    The engine still surges upon warm-up, but the vehicle otherwise has no problems. Now at 133,000 miles.
    So I googled "what causes an engine to surge at idle". This is what appears first -

    "If an engine is not getting enough fuel (this is called ďrunning leanĒ), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge." Sep 10, 2015

    Since you ruled out the vacuum leak, .........

    A bottle of Techron costs less than $5 @ Walmart.

    https://www.walmart.com/ip/Chevron-T...12-oz/46683811

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    I really hope itís not the fuel pump. I found some cheap gasoline additives at Dollar Tree, but it hasnít done anything



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