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Thread: CVT Failure (at 304,000 km / 189k miles, delivery vehicle)

  1. #71
    Radiators were punctured or defective?


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    Quote Originally Posted by Fummins View Post
    I never said it was great. But remember this is 10k econo car not a 60k toyota truck. That's kind of a ridiculous comparison. And for never having the transmission filter changed ever 190k isn't too bad. I'm curious if the tundra still has the original filter in the tranny or would it crap out at 200k as well if maintained the same?
    But we are expecting these to be lasting twice that. I'm hoping that if I change the filters once in a while along with all the extra fluid that pours out when the pan is pulled that the cvt should last much longer. Changing 2-3 quarts of fluid once in a while doesn't seem to do prevent failure as I'm pretty sure the case would be for most other transmissions.
    I'll be pulling the pans on a few other car's once I get the filters and gaskets and I'll post what I find.
    I'd say 190K is middle of the road for an economy car transmission. But to me it's a little concerning since my choices were between the Yaris and the Mirage. I'm pretty sure Yaris automatic transmissions get closer to 300K.

    Did the CVT give you any warnings that it was going to die or was it all of a sudden?

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        click to view fuel log View my fuel log 2014 Mirage 1.2 automatic: 39.7 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.6 mpg (Imp)


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    Quote Originally Posted by Fummins View Post
    The 14' spark we had weird problem that sounds similar to your's. The driver complained that the rpms would bounce. I drove it a few times and didn't notice anything wrong. The driver was adament something was wrong so I took it for a good long drive down the highway and noticed that while holding steady around 60-70mph the rps would bounce, not very noticeable unless you looked at the tach though. If you touched the gas just right it was easily to replicate and much more pronounced.
    That's sounds like exactly what mine is doing. It's almost like bouncing a ball. If you accelerate just right it makes the bouncing more obvious. I think my description of the problem was a little misleading when I said it occurred while accelerating, it's not like I had to floor it to make the problem happen. Just a slight acceleration is what usually causes it, or going up a hill. But the term "bounce" really hits the nail on the head. That's what I was trying to describe.

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        click to view fuel log View my fuel log 2014 Mirage 1.2 automatic: 39.7 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.6 mpg (Imp)


  4. #74
    Moderator inuvik's Avatar
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    Quote Originally Posted by Madison320 View Post
    That's sounds like exactly what mine is doing. It's almost like bouncing a ball. If you accelerate just right it makes the bouncing more obvious. I think my description of the problem was a little misleading when I said it occurred while accelerating, it's not like I had to floor it to make the problem happen. Just a slight acceleration is what usually causes it, or going up a hill. But the term "bounce" really hits the nail on the head. That's what I was trying to describe.
    The difference between the rpm's while cruise control is activated vs non cruise control driving is pretty pronounced. Without cruise control engage the CVT will vary rpm's much more than with cruise engaged.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


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    Quote Originally Posted by inuvik View Post
    The difference between the rpm's while cruise control is activated vs non cruise control driving is pretty pronounced. Without cruise control engage the CVT will vary rpm's much more than with cruise engaged.
    I'm used to the CVT fluctuating a little but this is different. It's like it gets stuck in a loop and it fluctuates from high to low, over and over and won't stop until you adjust the gas pedal a little.

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        click to view fuel log View my fuel log 2014 Mirage 1.2 automatic: 39.7 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.6 mpg (Imp)


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    Moderator Eggman's Avatar
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    I wonder if a sensor failure would cause this.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  7. #77
    Still Plays With Cars Loren's Avatar
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    Believe it or not, sometimes that sort of thing can be caused by weak (not bad enough to misfire, just weak) spark plugs. I just rectified the same problem in our driver's ed car. It's not a Mirage, and it has a normal 6-speed automatic transmission, but it was doing essentially the same thing. I'll try to explain.

    If your plugs are weak (and/or you've got dirty fuel injectors that aren't delivering SMALL amounts of fuel properly), at low load, such as when cruising or very gently accelerating, the fuel mixture just isn't going to fire quite as efficiently as it should. As a result, it's not making quite as much power as it should. So, what do you do? You give it a tiny bit more throttle. At some point, the ECU detects that you've created enough vacuum (by opening the throttle more) that it should downshift. That might not be what you wanted. You just wanted to keep cruising up that gentle slope, or maybe you were trying to gently accelerate from 40-45... but, you didn't want that downshift.

    This is what I was getting in the Kia. It drove "okay". No real problems. But, if I was cruising at a low RPM and trying to gently accelerate just a little bit, it would feel sluggish... I'd give it just a tiny bit more throttle, and it would downshift... and then immediately upshift again. Almost "hunting", but not quite. It took me a while to figure out what was going on. It just didn't feel like it was shifting right.

    First, I reset the ECU, thinking that maybe with a bunch of people driving the car, and lots of practicing parking and that sort of thing, maybe the transmission logic had learned some wonky shift points. That didn't help.

    Then we changed the spark plugs and ran some injector cleaner through it. That TOTALLY fixed it. The car feels much more responsive. I could tell the difference immediately. And it no longer hunts. You're going 50, you want to go 55... you lean on the throttle a little bit, and you get there, even if you're going uphill a little bit. It doesn't downshift on you unless you actually WANT it to.

    Now, again, this is a regular 6-speed automatic. But, I'd bet that the Mirage does the same thing. The CVT is essentially an automatic with something like 26 gear ratios rather than the usual 5 or 6. With more gear ratios, and such a subtle difference between, say... the top 3 gear ratios, the ECU is probably a LOT more sensitive as to when it thinks it should command a downshift.

    And if you're wondering, the Kia only has about 32,000 miles on it. And it had "100,000 mile" Iridium plugs. This is the second time I've had those kind of plugs decidedly NOT live up to their claimed potential. (the first time was with the Yaris at a race track... I started getting a repeatable CEL for high-rpm misfires on two cylinders... swapped the plugs around and the misfires followed... new plain-jane copper NGK spark plugs fixed the problem)

    So... think about a new set of spark plugs. Could be as simple as that.
    Simplify and add lightness.

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    Quote Originally Posted by Loren View Post
    Believe it or not, sometimes that sort of thing can be caused by weak (not bad enough to misfire, just weak) spark plugs. I just rectified the same problem in our driver's ed car. It's not a Mirage, and it has a normal 6-speed automatic transmission, but it was doing essentially the same thing. I'll try to explain.

    If your plugs are weak (and/or you've got dirty fuel injectors that aren't delivering SMALL amounts of fuel properly), at low load, such as when cruising or very gently accelerating, the fuel mixture just isn't going to fire quite as efficiently as it should. As a result, it's not making quite as much power as it should. So, what do you do? You give it a tiny bit more throttle. At some point, the ECU detects that you've created enough vacuum (by opening the throttle more) that it should downshift. That might not be what you wanted. You just wanted to keep cruising up that gentle slope, or maybe you were trying to gently accelerate from 40-45... but, you didn't want that downshift.

    This is what I was getting in the Kia. It drove "okay". No real problems. But, if I was cruising at a low RPM and trying to gently accelerate just a little bit, it would feel sluggish... I'd give it just a tiny bit more throttle, and it would downshift... and then immediately upshift again. Almost "hunting", but not quite. It took me a while to figure out what was going on. It just didn't feel like it was shifting right.

    First, I reset the ECU, thinking that maybe with a bunch of people driving the car, and lots of practicing parking and that sort of thing, maybe the transmission logic had learned some wonky shift points. That didn't help.

    Then we changed the spark plugs and ran some injector cleaner through it. That TOTALLY fixed it. The car feels much more responsive. I could tell the difference immediately. And it no longer hunts. You're going 50, you want to go 55... you lean on the throttle a little bit, and you get there, even if you're going uphill a little bit. It doesn't downshift on you unless you actually WANT it to.

    Now, again, this is a regular 6-speed automatic. But, I'd bet that the Mirage does the same thing. The CVT is essentially an automatic with something like 26 gear ratios rather than the usual 5 or 6. With more gear ratios, and such a subtle difference between, say... the top 3 gear ratios, the ECU is probably a LOT more sensitive as to when it thinks it should command a downshift.

    And if you're wondering, the Kia only has about 32,000 miles on it. And it had "100,000 mile" Iridium plugs. This is the second time I've had those kind of plugs decidedly NOT live up to their claimed potential. (the first time was with the Yaris at a race track... I started getting a repeatable CEL for high-rpm misfires on two cylinders... swapped the plugs around and the misfires followed... new plain-jane copper NGK spark plugs fixed the problem)

    So... think about a new set of spark plugs. Could be as simple as that.
    I'm starting to think that could be it. I've got a new set of plugs in the glovebox ready to install and I also was going to clean the injectors like you said. It sure can't hurt.

    Thanks!

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage 1.2 automatic: 39.7 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.6 mpg (Imp)


  10. #79
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    Quote Originally Posted by Fummins View Post
    I just had another cvt fail. This time at 223xxxkms. When you put the car in gear it feels like the torque converter is locked up and the car stalls. Like trying to drive away in 5th gear in a manual. I changed both filters about a week ago. I posted the pics of them on another thread. They were black, just like the fluid was but there weren't any pieces of metal in the pan.
    I'll keep you posted what I find with this one.
    I'm wondering if it's better to just change the fluid every 30k and not drop the pan and replace the filter. That's what the manufacturer recommends. Wouldn't it be in their best interest to recommend the routine that will make the CVT last longest? I'm assuming when they designed the CVT they tested it under many different scenarios to see which one last longest. Maybe it's designed to allow the shavings to accumulate at the bottom and the best curse of action is not to disturb the shavings?

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage 1.2 automatic: 39.7 mpg (US) ... 16.9 km/L ... 5.9 L/100 km ... 47.6 mpg (Imp)


  11. #80
    Still Plays With Cars Loren's Avatar
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    All Mitsubishi cares about is meeting legal requirements (emissions and safety and such) and not having to repair the car under warranty. "As long as possible" after that isn't really their concern. In fact, they should want it to blow up in a ball of fire at 110,000 miles so that you'll buy a new one after 8 or 10 trouble-free years!

    Seems like the key with all of these failures is that the fluid is black. Something is cooking the fluid. Either just natural aging of the additives in the fluid... or something mechanically causing slippage, friction and heat, and cooking the fluid.

    And if you can't change ALL of the fluid easily, then it does make sense to do a partial change more frequently.

    That's what I opted to do on my wife's Miata (2007). It's not a CVT, but it's a modern automatic that uses special unobtanium ATF. Mazda calls it a lifetime fill and lists absolutely NO service interval for the fluid. Typical automatic transmission, changing all of it is difficult. So, I opted to drop the pan, change the filter and change as much of the fluid as I could at 50k, and vowed to just pull the drain plug on the pan and change... maybe 2 quarts or whatever comes out... at every other oil change. (mind you, we do annual oil changes, maybe 6-8k miles typically)

    Keeping the special additives in the ATF fresh is what is most critical, I think. The oil itself is just basic hydraulic fluid. It will last forever as long as you don't overheat it. The additives are what's required to keep it from foaming, to give you just the right amount of friction between the CVT belt and drums, give you just the right amount of lubricity for all the moving parts, etc.


    Simplify and add lightness.

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