P0300 code: Is it the ignition coil or something else?

David_D73

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Hendersonville, Tennessee
A couple days ago my I went to turn on my 06 Jeep and it cranked but was making a weak sputtering sound, shaking the car. I suspected it was because of the cold weather and let it warm up and it went away within a few minutes. This morning I went to turn it on but I cranked it and again the weak sputtering continued but the car died. I cranked it again and revved the engine to keep it from dying (I know that's bad but I had to get to school).

I suspected either the ignition coil or spark plugs were bad after doing a little bit of research. I went to check the codes after getting home and code P0300 popped up and my suspicion was confirmed. I checked the spark plugs to see if any looked in bad condition and they all were in rough shape. I went to buy some replacement ones, I went with NGK. but once I installed them and turned the car on to crank it, the sputtering happened for a couple seconds and went away. Is it the ignition coil or something else? Its a 2006 4L 6 cylinder wrangler x for reference.
 
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A couple days ago my I went to turn on my 06 Jeep and it cranked but was making a weak sputtering sound, shaking the car. I suspected it was because of the cold weather and let it warm up and it went away within a few minutes. This morning I went to turn it on but I cranked it and again the weak sputtering continued but the car died. I cranked it again and revved the engine to keep it from dying (I know that's bad but I had to get to school). I suspected either the ignition coil or spark plugs were bad after doing a little bit of research. I went to check the codes after getting home and code 0300 popped up and my suspicion was confirmed. I checked the spark plugs to see if any looked in bad condition and they all were in rough shape. I went to buy some replacement ones, I went with NGK. but once I installed them and turned the car on to crank it, the sputtering happened for a couple seconds and went away. Is it the ignition coil or something else? Its a 2006 4L 6 cylinder wrangler x for reference.
P0300 is a misfire
Did you use antiseize on the spark plugs? sometimes it can get into near the tip and cause a misfire, I would also check your coils and wiring to make sure nothing is loose/somewhere its not supposed to be. Perhaps @Jerry Bransford can help. Jerry, do you think a bad o2 sensor could cause a misfire as well? This could also be a heat soak issue from my understanding
 
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Definitely not caused by a bad O2 sensor, those can only cause problems once the engine has started to warm up.The computer pays no attention to the O2 sensors when the engine is cold.

When first starting the engine David, does your temperature gauge register a normal cold indication, pointer at the lower end of the scale?
 
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It does indicate a cold temp when starting it in the morning. I did not put antisieze on any of the new spark plugs. I have been having problems with one of my o2 sensors. I replaced it 3 times but it wouldn’t go away so we took it to the dealership and they said it was the PCM. I ordered a new one acouple days before this started. It should arrive today or tomorrow from @Wranglerfix.
 
Sorry for the delayed update. I installed all new spark plugs Saturday night to see if it would fix the problem of the engine having a weak start. It did not. So on Sunday I also went ahead and tried a new ignition coil and that seemed to fix the problem. It has started perfectly for the past couple days just like before. Sunday afternoon I spent the day working on the Jeep. I installed the PCM and works great, got rid of my p0161 problem. I changed the oil and oil filter and installed a sub I got. But another problem came up. So Monday the check engine light was off all day. But Tuesday on my way to B-dubs after taking the ACT I saw the moment the check engine light came on. The new code is p0431. I did a little research and was going to switch out the o2 sensor to see if its not working properly.
 
So I checked the codes other day to see if changing the o2 sensor would change them. It read 133, 153, and 431. I changed the o2 sensor and drive alittle bit then checked the codes and they were the same so I changed it back and there still the same. What can I do or do I just have to take it in to the shop??
 
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A couple days ago my I went to turn on my 06 Jeep and it cranked but was making a weak sputtering sound, shaking the car. I suspected it was because of the cold weather and let it warm up and it went away within a few minutes. This morning I went to turn it on but I cranked it and again the weak sputtering continued but the car died. I cranked it again and revved the engine to keep it from dying (I know that's bad but I had to get to school).

I suspected either the ignition coil or spark plugs were bad after doing a little bit of research. I went to check the codes after getting home and code P0300 popped up and my suspicion was confirmed. I checked the spark plugs to see if any looked in bad condition and they all were in rough shape. I went to buy some replacement ones, I went with NGK. but once I installed them and turned the car on to crank it, the sputtering happened for a couple seconds and went away. Is it the ignition coil or something else? Its a 2006 4L 6 cylinder wrangler x for reference.
I had this a few weeks ago. Change plugs and now fixed.
 
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