P0303

[wrigley]

2023 5.7L with 43,000 miles. About a week ago I noticed a rougher idle. The next day I got a CEL and the code was P0303. The code was cleared and everything was fine for about a day and a half then the CEL came back on. A few hours later it went off, and has stayed off since. I realize there are numerous things that could cause this, but is BAD GAS one of them?

 

[Fast69Mopar]

2023 5.7L with 43,000 miles. About a week ago I noticed a rougher idle. The next day I got a CEL and the code was P0303. The code was cleared and everything was fine for about a day and a half then the CEL came back on. A few hours later it went off, and has stayed off since. I realize there are numerous things that could cause this, but is BAD GAS one of them?

If this were a bad fuel situation I would expect to see a P0300 Multiple Cylinder Misfire set as well.

Now, with this being a 5.7 HEMI the first thing I check for with a misfire code is a failed lifter and a subsequent damaged cam lobe. You can do your due diligence first and inspect the spark plug on cylinder #3 and then perform a compression test and then a leak down test.

If those test are good then you can move the spark plug to an adjacent cylinder and see if the Misfire follows the spark plug. Then move the ignition coil to the next cylinder and see if the Misfire follows it as well.

If those test give good results I would remove the left bank rocker cover and bar the engine over and watch the pushrod movement and spring movement to verify that they are equal to the next cylinder.