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I have a Ford Focus 1.6 LX 16v 2004 MK1. I went away for one month and after I returned the battery was dead. I charged the battery, started the engine and took it for a short drive. I noticed it was chugging a bit so I took it for a long and fast ride thinking it might be moisture but the chugging still persists. I bought a diagnostics reader which gave out a P0302 (cylinder 2 misfiring) error code.

It was absolutely fine before I went away. Could it be the fuel injector has got clogged?

I swapped over the ignition lead & sprk plug but still reads the error from cylinder 2.

What should I try next?

Thanks and hope you can help.

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  • If you are using gas with alcohol, the alcohol may have separated from the gas and is being burned all by itself (lean misfire), I would top off with fresh gas and drive it a few miles to see if it stops misfiring.
    – Moab
    Commented May 25, 2020 at 12:07

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Ethanol is hygroscopic, meaning it absorbs water, if there was moisture in your tank it could have mixed with the fuel and contaminated it. Mixing in fresh fuel may help the situation. However, if fuel was the problem there would probably be misfiring in more than one cylinder, however there's no harm in trying.

I'd still be concerned about spark, replacing the plug and lead isn't necessarily going to fix that, I'd test for spark and then look at the coil if you aren't getting spark. Once you have verified you have a good spark I would try swapping injectors with another cylinder, if problem follows the injector then you need to try and clean it or replace it, if it follows the cylinder something else is wrong.

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    Swapping coils first is a better place to start. It's in the diagnostic chain and is a lot easier to accomplish than swapping an injector. Coils go bad a lot more often then injectors.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented May 25, 2020 at 14:27
  • Good spot @Pᴀᴜʟsᴛᴇʀ2, I wrote it out of order for sure. I've fixed that.
    – GdD
    Commented May 25, 2020 at 17:17
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    Also, easy test for injector is to pull the injector wiring and check for it running differently. Whenever you pull an injector you really should put new o-rings on them as these can easily be damaged during the removal/re-install process. You don't want errant fuel being spewed all over the engine bay if one should leak.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented May 25, 2020 at 18:57

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