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I have a misfiring cylinder on my 2009 Ford Ranger 2.3L 4 cylinder engine.

I'll leave diagnosing the cause of the misfire to another thread, but I suspect it's related to retapping one of the spark plug ports last year (without removing the head).

I noticed the misfire starting during a weekend road trip last week - the truck would shudder going up hill below 2000 RPM or so. The problem got worse this week and the check engine light came on. The only code is 0302 - misfire cylinder 2.

I tried a couple easy things to diagnose the problem and reset the error codes each time. What I noticed is that after I reset the code, the truck has the shuddering problem, I can feel the misfires. But then after the engine light comes on it seems smoother - but with a noticeable lack of power.

Is it possible that the engine control module is just disabling that cylinder because it's misfiring so consistently?

And if so, does this mitigate the risks of driving the vehicle with a misfiring cylinder? Eg. if the cylinder has been disabled, it isn't sending unburnt fuel mix to the catalytic converter?

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  • Welcome to Motor Vehicle Maintenance & Repair! I'd suspect if it clears up after the code, it's going into a different mode and has nothing to do with your ignition. Off the top of my head I'd suspect something like the MAF is having issues at which point it goes into open loop mode and things smooth out. To my knowledge, ECU's will not deactivate cylinders like you're suggesting. What exact codes are you getting? Nov 17, 2022 at 19:23
  • Okay that's interesting @Pᴀᴜʟsᴛᴇʀ2. The only code I'm getting is 0302.
    – Adam Brown
    Nov 17, 2022 at 19:34
  • One of the things that can happen with a misfire is that raw fuel can be dumped into the exhaust. This can very quickly overheat and damage the catalytic converter and other nearby components. Some ECUs do disable the fuel into a misfiring cylinder to help prevent this damage. I'm not sure about your Ranger but it is something that can and is done. The problem may be the ignition coil. You might try swapping the one from the misfiring cylinder with another cylinder and see if the problem follows.
    – jwh20
    Nov 17, 2022 at 20:16

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No, the computer would not disable the cylinder due to misfiring. That would make the engine run absolutely horribly at idle, and with 1/4 the power missing, probably shake the engine right off its mounts when you are trying to accelerate onto the freeway.

The misfires are most likely intermittent.

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  • This answer is a bit inaccurate. ECU's do disable injectors quite often when they detect certain conditions like misfire or issue with spark on a cylinder. Some cut off both coil+injector but just the injector is more common.
    – narkeleptk
    Apr 17, 2023 at 19:47
  • @narkeleptk How do they resolve the monstrous driveability problem that would create at idle? Knock out the opposite cylinder also? Apr 17, 2023 at 20:06

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