Background - 2012 Non-S Auto. 49k miles. No issues prior to changing the oil.

Changed the oil myself and overfilled it by 0.5qt, drove over 200 miles before extracting the extra out. During which I accidentally filled it with 89 gas.

Symptom of the issue: CEL would come on when accelerate hard (6k RPM). When the lightY(yellow, non-flashing CEL) comes on, idle would be rough and acceleration suffers. Clearing the fault codes (P0304 and P0300) via OBDII would smooth the idle and remove the acceleration bog immediately. No problem with gradual acceleration, even up to 85mph.

My first thought is the less than optimal gas causing misfire. However, 2 full tanks of 93 gas have passed and the issue still comes up with the mentioned hard acceleration.

The car has extended manufacturer warranty. Going to take it in on Friday, but would like to know if there is some simple fix.

 

Have you replaced the spark plugs yet? If not I would start there, the Coopers seem to destroy spark plugs in under 50K (they're rated for 100K).

Detroit Tuned NGK Spark Plugs

 

Good call nkfry. It was indeed the spark plugs!

 

Glad it was a quick fix, we see enough problems with Coopers and sparkplugs that if you're having a misfire problem and are over 35k miles chances are that you need plugs.

 

what should the gap be?

i replaced two coil packs and 4 plugs after a limp mode and running great but misses under throttle how cani clear the maps in the ecm?