P0300, P0302, and P0304 Misfire, HELP! - Kia Forum
 
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post #1 of 6 (permalink) Old 01-05-2017, 06:34 PM Thread Starter
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Exclamation P0300, P0302, and P0304 Misfire, HELP!

I have reached my wits end with this issue. I have a 2010 Kia Rio LX and it has been experiencing some engine problems. I've had the codes scanned and it reads a P0300, P0302, and P0304 misfire. Before the problem got worse, the engine light would flash (misfire) at start up and the light would remain on while driving. It had a slight loss of power with the engine shaking rough enough to feel it, however the shaking settled down as the vehicle reached high speeds.

As it got worse, I began to experience a huge loss of power. During acceleration, the rpm would reach to about 3.25, with the engine ceasing the shake, then mellow out to a 2.8 going 68 m/hr with the engine shaking. The last time I drove it, the shaking worsened exponentially continued to misfire with little to no power. I haven't driven it since.

I had one mechanic check it out in November before it got worse, and when he removed the coil and spark plugs from cylinder 2 and 4, the spark plugs had 2 years of wear on them, even though I had changed them around May of 2016. I had another mechanic check it out (just took a look at the engines performance, and nothing else) and he suggested it might be a bad coil pack and that the engine is fine.

I can't get it to a shop, so if the problem could be fixed by a freelance mechanic, that would be great. I rather figure out what's wrong with it first before I get it fixed. Any and all help is appreciated.

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post #2 of 6 (permalink) Old 01-05-2017, 10:48 PM
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Originally Posted by ayanasioux View Post
I... the spark plugs had 2 years of wear on them, even though I had changed them around May of 2016. ....
How had it been running before you replaced the factory spark plugs? Which plug did you install?
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post #3 of 6 (permalink) Old 01-09-2017, 09:09 AM
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Normally multiple misfire code(s) is an engine related problem that affects all cylinders, eg vacuum leak, poor fuel supply. The ecm knows the amount of advance the engine will receive after a plug fires, but if that advance is not met, the cel comes on.
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post #4 of 6 (permalink) Old 01-09-2017, 01:40 PM Thread Starter
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Originally Posted by kiaguy002 View Post
How had it been running before you replaced the factory spark plugs? Which plug did you install?
Sorry for the late reply. Before I replaced all the plugs and coils, it was misfiring, rough idle, jerking from acceleration, and sometimes it would just flat out stop. It got so bad that it wouldn't go faster than 40 miles/hr. Once I replaced everything, it was running like new. But according to what you're saying, it's probably a vacuum leak. I suspected the same before, but I wasn't sure.
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post #5 of 6 (permalink) Old 01-09-2017, 01:43 PM Thread Starter
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Originally Posted by turbonut View Post
Normally multiple misfire code(s) is an engine related problem that affects all cylinders, eg vacuum leak, poor fuel supply. The ecm knows the amount of advance the engine will receive after a plug fires, but if that advance is not met, the cel comes on.
However, the only reason why I didn't think it was a vacuum leak was because it wasn't making any hissing noise. The only thing that happened was the engine was shaking vigorously with poor power and fuel economy.
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post #6 of 6 (permalink) Old 01-09-2017, 02:10 PM
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Originally Posted by ayanasioux View Post
However, the only reason why I didn't think it was a vacuum leak was because it wasn't making any hissing noise. The only thing that happened was the engine was shaking vigorously with poor power and fuel economy.
Do you have access to a Live Data Scanner?

Check the O2 for switching, with no bias, and the STFT?LTFT..

Post info and the freeze frame data..

... Philip
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