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I currently have an engine code for P0449 which I have another thread for and I believe I have the fix for it (waiting on weather to improve to change the EVAP Vent Solenoid).

However, today I started the car up and it idled very rough and the check engine light began flashing, my "Service Stabilitrak" warning and light came on. After about 15-20 seconds the engine smoothed out and when I pulled it into the garage the Stabilitrak warning had gone away, and the CEL stayed solid. I read the code and got P0300 for multiple cylinder misfire. I then took it on a few mile drive and ran it up to 80mph with no issues. I didn't get any sort of hesitation at all, no strange sounds, nothing.

I'm wondering if this could be a side-effect of my P0449 code, and if anyone else has had this issue. I've had the car rough idle on me once before, however it never threw a code and it only lasted for about 5 seconds.

I may change the plugs, but it really looks like a PITA on this 3.6 V6.
 

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I currently have an engine code for P0449 which I have another thread for and I believe I have the fix for it (waiting on weather to improve to change the EVAP Vent Solenoid).

However, today I started the car up and it idled very rough and the check engine light began flashing, my "Service Stabilitrak" warning and light came on. After about 15-20 seconds the engine smoothed out and when I pulled it into the garage the Stabilitrak warning had gone away, and the CEL stayed solid. I read the code and got P0300 for multiple cylinder misfire. I then took it on a few mile drive and ran it up to 80mph with no issues. I didn't get any sort of hesitation at all, no strange sounds, nothing.

I'm wondering if this could be a side-effect of my P0449 code, and if anyone else has had this issue. I've had the car rough idle on me once before, however it never threw a code and it only lasted for about 5 seconds.

I may change the plugs, but it really looks like a PITA on this 3.6 V6.
I currently have an engine code for P0449 which I have another thread for and I believe I have the fix for it (waiting on weather to improve to change the EVAP Vent Solenoid).

However, today I started the car up and it idled very rough and the check engine light began flashing, my "Service Stabilitrak" warning and light came on. After about 15-20 seconds the engine smoothed out and when I pulled it into the garage the Stabilitrak warning had gone away, and the CEL stayed solid. I read the code and got P0300 for multiple cylinder misfire. I then took it on a few mile drive and ran it up to 80mph with no issues. I didn't get any sort of hesitation at all, no strange sounds, nothing.

I'm wondering if this could be a side-effect of my P0449 code, and if anyone else has had this issue. I've had the car rough idle on me once before, however it never threw a code and it only lasted for about 5 seconds.

I may change the plugs, but it really looks like a PITA on this 3.6 V6.
I actually have a 2015 chevy impala LTZ and I’ve been battling with dealers about this p0300 code as well. For about 3 weeks now this thing starts up, everything sounds ok, rpm’s drop down below 1krpm like it should, but as it starts to warm up the engine starts shaking/misfiring causing stabilitrak light to come on, as well as flashing check engine light. After a few seconds of it doing that, it stops and smooths out. Few seconds later, everything repeats, until it’s reached operating temp. It does not do this while at operating temp. Mainly does this after I drive it, let it cool down for a while then start it back up. Here and there I have 0 engine power as well. I hope you’re able to figure out your problem, as I’m trying to figure out mine myself. Let me know what you find out!
 

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I actually have a 2015 chevy impala LTZ and I’ve been battling with dealers about this p0300 code as well. For about 3 weeks now this thing starts up, everything sounds ok, rpm’s drop down below 1krpm like it should, but as it starts to warm up the engine starts shaking/misfiring causing stabilitrak light to come on, as well as flashing check engine light. After a few seconds of it doing that, it stops and smooths out. Few seconds later, everything repeats, until it’s reached operating temp. It does not do this while at operating temp. Mainly does this after I drive it, let it cool down for a while then start it back up. Here and there I have 0 engine power as well. I hope you’re able to figure out your problem, as I’m trying to figure out mine myself. Let me know what you find out!


Original post is 2 1/2 years old.

What codes are set for your vehicle?

If the evaporative vent solenoid is stuck open, it can cause a rough idle, no power and misfire at startup. This is caused by excessive fuel vapor fumes being drawn into the engine, causing a rich condition.

When the fumes burn off and the engine warms up, it runs fine.

Do not drive the vehicle with a flashing check-engine light, as it indicates a serious misfire which can quickly cause engine damage and/or damage to the catalytic converters (due to unburned fuel).
 
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