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Discussion Starter #1 (Edited)
CEL Engine misfire,seems ok after spark plugs change,but still got a softer problem

I have another thread of this issue but not many answers. I have a my12 Ampera with 84k km, I had once last year a CEL starting the car in winter at -15C and I guessed it was a bad fuel, clear the error in service and no problem since this year.
Now I had intermitent problems starting negative temps of winter and I got the CEL with error code P0300 - Random Cylinder Misfire especially on mornings.
It works 95% good but randomly I get like bad fuel feeling, car start to run interupted then CEL blink then steady orange. I've tried put a half tank of fresh fuel but no result. So I talk to the mechanic and tell me it sound like something to do with ignition, almost certenly spark plugs. I change them and notice that engine light turn off after second start of the car. Car runt fine for a week, one time only blink for 3 seconds and that was the first sign that the problem was not solved. On MM it start to shake really bad when stationary, some days works just fine, today I drive 70km on gas with no probles. At night I notice some vibration when stationary, no CEL blinking but not running as smooth as it supose to. I have an appointment for a diagnose on monday, but i really don't know what may cause this. I understand if it was the coil , it would run bad all the time, like really bad. Consumtion is like 9% on this weather so not bad at all.
Anyone with same problem around here?
 

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I wouldn't say if it was a coil, it would run bad all the time. Failing coils can be temperature sensitive. Any time you make an assumption, you could be going down the garden path.
 

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Discussion Starter #3
For now, the engine light has dissapeared, the car works fine after about 150 driving in last week. I will see if the problem got back on negative temps. If so, then maybe the coil act bad on moisture/freeze...But if the coil was bad I don't think the engine light would turn off, because if it detect any misfire on the last 7 cycles ,than the engine light wouldn't turn off.
 

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Discussion Starter #4
Just got back from service
Today was raining when I drove to the dealer service and just before getting there, a blinking CEL for 3 sec then dissapear. They put the tester on the car and found only history faults, can't duplicate the problem there. Code P0300 was confirmed Randon cylinder misfire and show me that misfire are not only or one or two cylinder but all of them, cyl 1 only less then others. 3 weeks ago i've changed the spark plugs but didn't clear the faults so since then the car drive 95% good, but not perfect. The say a bad coil couldn'd make misfire on multiple cylinder at once. Conclusion was to drive with the remaining fuel until low then refill from another gas statoin, matbe the fuel was bad. I once put like 15l on top of existing one, drive well but today again I got a blinking CEL.
On my observation I notice is happening on wet roads or after washing the car, maybe it's a coincidence...maybe not
IMG_4393.jpg
 

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On my observation I notice is happening on wet roads or after washing the car, maybe it's a coincidence...maybe not
View attachment 160251
If this was 20 years ago, I'd tell you to replace the distributor cap.

I would visually inspect ground straps and replace any that look suspect.

I would also inspect the PCV system.

I would not worry about any of it until I ruled out the potential for bad fuel.
 

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Discussion Starter #6
Thank you for your prompt answer!
I don't know where to look for ground straps and also don't know what is PCV system.
Problem with ground makes sence because after I wash the car sometimes when it stays in steam I cannot charge and my charger error show me error 3 3 1 (ground or negative problems on car). This could cause the coil acting bad?
 

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The charging issue is a separate problem. Probably a crack in the charger circuit board where you plug in. The misfire issue cannot be a single coil. Modern GM engines use multiple coils, one per cylinder. So the technicians diagnosis of bad fuel could be correct. The PCV, positive crankcase ventilation, system directs crankcase fumes into the air inlet instead of the atmosphere reducing pollution. These fumes sometimes coat the fuel injectors with a tar like substance causing misfires.
 

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Thank you for your prompt answer!
I don't know where to look for ground straps and also don't know what is PCV system.
Problem with ground makes sence because after I wash the car sometimes when it stays in steam I cannot charge and my charger error show me error 3 3 1 (ground or negative problems on car). This could cause the coil acting bad?
Bad ground straps can cause lots of problems that are seemingly unrelated.

I have a gen 2 Volt, so I can't give you detailed directions, but here's the diagram for a gen 1 Volt from the parts catalog:

ground.jpg

The ground straps are number 3 and 4.
 

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I will just throw some guesses out into the mix. Could this possibly be caused by low fuel pressure due to a weak fuel pump or clogged fuel filter? I am also wondering about having some water in the fuel tank.
 

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Discussion Starter #10
But that service diagnose shouldn't tell me if something was wrong at some point in the logs? I mean a bad ground or low pressure on fuel pump? I guess it shows another code instead of P0300?
 
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