P0300 random cylinder misfire code with no symptoms?

[Brian35XR]

Anyone ever deal with a P0300 code that keeps popping up after being cleared? The code is for "Random/multiple Cylinder Misfire Detected".

I did some searching and it seems like this code is usually accompanied by other codes (O2 codes, crank/cam sensor codes, etc..) which usually point to what the issue is. In my case this is the only code firing. Mechanically the car runs fine - idling, accelerating, cruising, etc.. are all smooth.

The only things that changed recently was around 6 months ago my alternator burnt out which I had replaced. In doing I also had 4 pulleys replaced because they were dry and whining. I've driven thousands of miles since then and the code only popped up recently. I even read sometimes this could be caused by the VVEL if your oil is dirty, and I haven't changed mine in awhile.

Anyone have any ideas or ever experienced this code on their M37? Thanks!

[VStar650CL]

Unfortunately your '11 doesn't store a misfire history like later models, but there should be Freeze Frame data stored in the ECM for the latest instance when the code occurred. There about a zillion things which can cause a slight, random misfire, so It will help enormously to know the engine RPM and temperature. If you can clear the code repeatedly and get a series of FF's for it, that will help even more.

[Brian35XR]

Unfortunately your '11 doesn't store a misfire history like later models, but there should be Freeze Frame data stored in the ECM for the latest instance when the code occurred. There about a zillion things which can cause a slight, random misfire, so It will help enormously to know the engine RPM and temperature. If you can clear the code repeatedly and get a series of FF's for it, that will help even more.

Thanks for.your response VStar. I only have one freeze frame since i cleared the codes prior to the last one. For what it's worth - i only ever get this code when i first start the car; it doesn't ever just fire randomly while I'm driving.

This shows the temperature and RPM are low... Anything else pop out to you that i can investigate?


Edit: Uploaded a better screenshot for the 3rd time!

[VStar650CL]

From what I see there, it looks like the misfire is occurring on drop-throttle at low RPM's. At 86F coolant temp, the A/F (wideband) sensors will just be fully warm, so the engine probably just went from open to closed loop immediately before the code occurred. Because of the dropped throttle, it's hard to tell if the A/F readings mean anything. They probably don't, spiking lean (purposely) is a normal part of dropping the gas pedal. I'd say start by having a look at a spark plug on each bank and see if maybe they're running cold.