548chevelle

After a 20 minute drive in my '11 to get the oil hot I drained it, replaced the filter and oil. Started it up, checked for leaks and when I took it for a test drive got the P 0300 code for the first time ever. And there was just a cartoon in the newspaper. Two mechanics are looking under the hood of a car and they see a couple of "check engine light fairies" messing with the engine. Anyway I looked up the possible causes- plugs, wires, vacuum leak, etc etc. But I also see that the way the ecm detects a problem is by measuring the time between cylinder firings. A miss causes a variation in the time between cylinder firings. I have a Mantic clutch which causes my tranny to rattle at idle. I noticed when I first start the engine and it idles at 1000 theres no rattle so i raised the idle from 650 to 750 which helped somewhat. So I'm wondering if when I let it idle for a few minutes to check for leaks the ecm picked up the rattle as an engine misfire. Now how do you clear the code? I have an Intune and a scan tool and neither cleared the code. I'll save battery disconnect as a last resort.

atljar

Mantic here too.. I seriously doubt that will cause misfires. Is the code currently present or history code? If history code, any OBD2 scanner should clear it. If its current, you can try to clear and it likely will go off for a second and then the light will come right back.

Some of the more expensive scan tools can show you power balance on the cylinders, and if you do have a true misfire help you to isolate the issue.

rio95

If you have a cam you probably need to adjust the tables in the tune for this code. Very common.

JP426