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Anyone else get the P0300 Random Misfire CEL? At first it flashed, ran rough until I pulled over. Turned the car off and back on and it was fine. That was the initial incident. Now when it gets to about 15 miles left on battery, I switch to Mountain mode to save some battery in case it becomes an issue again. The engine works fine most of the time but occasionally start flashing the CEL P0300 code again. When it does, I turn off Mountain mode and go back to battery and then back to mountain mode and the engine is fine. If you had this problem what was your fix? 87,000 miles here and out of warranty. I can change the plugs and coil pack myself in case I have a bad coil pack or fouled plug. Be interesting to hear what the fix was for others who experienced this. Thanks so much.
 

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Replaced plugs and coil pack for P0301 code

Just had this happen to me yesterday. I had the P0301 code which is for #1 cylinder misfire and P0300. My 2013 Volt has 39000 total miles with about 10000 miles on the engine. I replaced all 4 plugs and the coil pack (these new coil packs are one unit for all 4 plugs). Super easy job took about an hour. I got the parts at the dealer for $190. Rockauto.com has the parts for about $105. I just could not wait so I paid the dealer premium. I never really noticed the engine running rough. So far I logged about 15 miles on the engine and everything seems to be good to go. No check engine lights or roughness. Good luck to you.
 

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Well my luck is not so good. Today after about 30 miles of gas engine run time, the P0301 code is now back. The engine seems to be running smooth and I really don't sense any problems. Back to the drawing board. I'll probably end up taking it to my dealer, but maybe I can find something else? Injector possibly?
 

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Sorry it didn't work out for you. I was thinking that 15 miles wasn't a suitable test period.

You might try adding 3 gallons of E85 as a fuel system cleaner (top off tank with 87 octane). That would get you about 30 to 35% ethanol, which won't cause any problems. You'd have to double that to get a check engine light.
 

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Update....I removed and reinstalled the new coil pack ensuring the leads on the coil were not out of place and actually touching the spark plug. I cleared the check engine light, but this time I put in the Volt in "Service Mode" before clearing. This might have been the trick. I've driven about 100 miles on the gas engine with no problems or check engine. I'm going to say for now that this problem seems to be fixed. Happy again! I'm glad all those years turning a wrench as an aircraft mechanic and shade tree auto mechanic are helping me today. I'm dreaming of the day I don't have to mess with any gas engines. Model 3 please come soon...
 

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For anyone interested, a great place I start looking is at fuel trims. If you aren't sure what is going on, it is easy to rule out items since a misfire could be the result of a vacuum leak, injector, or ignition issue. I'll start a new thread with some info on this who might want to direct their diagnostic approach instead of changing parts and hoping for the best.



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Reviving an old thread, however since I had the same issue, I though Id report my fix here. 2012 Volt that gets a flashing cel followed by an intermittent engine misfire that shakes the whole car (feels like possible transmision issues). The issue seemed to come and go for no reason. My problem was that when I removed the coil pack assy., cyl 1&2 spark plug holes were very dirty with a bit of water pooled up in cyl 2. I used compressed air to dry out the spark plug hole, reassembled and all is normal again. Please give this a try before going to the dealer as they may want to replace at least the coil pack in order to make a quick buck (As a retired tech, I dont trust mechanics and only have shops service my vehicle when I don't have the tools to do it myself). Hope this helps someone since when I initially searched the internet, all posts seemed to point to a cracked head.
 

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Hi Skottk, I see this is an old Thread but I just got back from service where I changed Spark plugs on my12 Opel Ampera. It has 80k km and since starting Winter with temp below 0 I get P0300 error code, Random Misfire. So I change the spark plugs, car works great, engine light turn off after second start. After 5km on way home I speed up to catch a green light and rev to 4500rmp I guess, so after 100m car start shaking and CEL binnk few times then stoped. Then I drove the car on highway to test it on speed, no problem for about 40km. You seems to have the same situation when you changed your spark plughs then after a while same simtoms reapear... Any sugestion? Did you since then run in to the same problem? My car does shake only on cold start then work normaly...thats why a year ago one day on -20c got the same problem but ignore it until this year. I also blame it on BAD FUEL(combined with spark plugs), maybe some still make problem but the car feels more normal after changing spark plugs, for shore.
 

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Hi Skottk, I see this is an old Thread but I just got back from service where I changed Spark plugs on my12 Opel Ampera. It has 80k km and since starting Winter with temp below 0 I get P0300 error code, Random Misfire. So I change the spark plugs, car works great, engine light turn off after second start. After 5km on way home I speed up to catch a green light and rev to 4500rmp I guess, so after 100m car start shaking and CEL binnk few times then stoped. Then I drove the car on highway to test it on speed, no problem for about 40km. You seems to have the same situation when you changed your spark plughs then after a while same simtoms reapear... Any sugestion? Did you since then run in to the same problem? My car does shake only on cold start then work normaly...thats why a year ago one day on -20c got the same problem but ignore it until this year. I also blame it on BAD FUEL(combined with spark plugs), maybe some still make problem but the car feels more normal after changing spark plugs, for shore.
how did the spark plugs look?you have a pick of them?
I know I got a misfire once in my volt,it was caused by the bad boat gas I put in it.the gas had a small amount of water in it.ran fresh hi test thru it and problem went away for good.
boat was another story,had to get rid of 125gal of some nasty looking gas.stuff never did separate even after a month of sitting.hated to waste the gas,killed me.
 

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When talking about bad gas I'm always reminded of the TV series Ice Pilots NWT. They (a pilot and mechanic) went from Yellowknife to Gimli to pick up a DC3 that had been sitting for a year. It wouldn't start. They drained some of the Avgas gas and poured it on the snow and tried to light it with a flare. It wouldn't burn. They drained the gas tank, filled it with fresh fuel, it started right away and flew all the way back to Yellowknife with no problems.
 

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I still got the problem but way less than before changing the spark plugs. Drive 150km with no problem then foar few sec CEL blink...Till starting the problem I put like 25L of fresh fuel over the old one. From service I've got no solution and the problem cannot be duplicated when diagnose the car....told me it cannot be the coil because I've got cylinder 2,3,4 and less on 1st randomly misfire, if it was the coil then only one should make problem...I'm not the expert. Hope to find some solution here. Many guesses around....
I attached the pictures from spark plugs... IMG_4090.jpg IMG_4091.jpg
 
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