I'm going insane. My 2007 cls550 with 130,000 Miles has been having an intermittent misfire for over a year now. I'll get a p0300 and a p0306. It will idle rough but drive fine. I've replaced the #6 cyl sparkplug. The coil. And recently the fuel injector. I thought the injector fixed the problem because it went 28 days and 600 miles after that before I went out and started the car and it was idling rough. Checked the codes and same thing . 0300 and 0306. Such a ler down. It usually goes a few days without issue then boom the rough idle and codes come back. She has plenty of power and no issues while driving. I haven't bothered checking compression because I figure a problem with compression wouldn't be intermittent and I'd feel some sort of power loss. To me this seems maybe electrical.

Since it's giving me a 0300 along with 0306 does that mean not just the number 6 cylinder? My scanner is one of those orange launch creader bi directional scanners. I'm trying to see if I can find the fuel pressure readings son the scanner.

Anyhow anything else I should be checking. Lke i said after replacing the injector it went 600 miles and 28 days without issue out of that mileage there was 2 one way trips of 90 miles. The rest of the miles during that time was multiple in town driving.

A lot of times when it's idling rough if I just shut the car off and back on na couple times it goes back to idlling smoothly.

I just wish if would mess up and stay messed up and give me more of a direction to investigate.