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Thread: Misfire under load with no CEL

  1. #1

    Misfire under load with no CEL

    Hey guys, I'm having an ongoing issue with misfires that I'm trying to track down.

    What happens:

    Under load, particularly when going up a hill, the engine will misfire a lot at between 2700-3300 RPM. This gets particularly bad on cold and wet mornings and reduces when engine warms up. If I put the transmission in manual mode and drop it down a gear or two to bump up the rpm past this range it runs fine until the rpm drops down into this range again.

    What I've done to fix this:

    replaced MAF sensor, no change
    replaced coil packs and plugs, no change

    Any ideas what to try next? I would think fuel system, but wouldn't the fact that it runs smoothly if I can get the RPM past this range rule that out?

  2. #2
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    2015 Mazda 6

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    May 2018
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    Quote Originally Posted by Canada_CX7 View Post
    Hey guys, I'm having an ongoing issue with misfires that I'm trying to track down.

    What happens:

    Under load, particularly when going up a hill, the engine will misfire a lot at between 2700-3300 RPM. This gets particularly bad on cold and wet mornings and reduces when engine warms up. If I put the transmission in manual mode and drop it down a gear or two to bump up the rpm past this range it runs fine until the rpm drops down into this range again.

    What I've done to fix this:

    replaced MAF sensor, no change
    replaced coil packs and plugs, no change

    Any ideas what to try next? I would think fuel system, but wouldn't the fact that it runs smoothly if I can get the RPM past this range rule that out?
    I had the exact same symptoms as you with a faulty ignition coil on my BMW 528i. very strange that the coil pack replacement did not fix your issue. even more strange still that you do not have a misfire code.

    honestly, my only other guess would be fuel injector(s)

  3. #3
    Yeah the most annoying part is the no CEL.... actually I had thought to check the injectors, so maybe that's why I'll have a look at next. I forgot to mention in my previous post that I have tried running injector cleaner through the system a couple of times to no avail, but that doesn't necessarily discount the possibility of an injector issue.

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