Random/multiple misfire.

What causes this? Can a vacuum leak do this? My idle is still not smooth. It is, but then when the car gets fully warmed up the TC lockup starts messing up, and I check the pending codes and there's the p0300. Clear it and it's fine until it throws the code again, usually not until it's warmed up.

So again, is there a checklist for causes?
Is there a checklist for vacuum leaks? I don't know where ALL the lines are.

 

The ol' P0300 code has been the bane of many posters here. Unfortunately, most do not post the answer to the cause they found. I had it once, and it was a plug wire had worked loose from the plug. It would only miss when it was raining. Start by checking plugs and wires. If you have an enhanced OBDII scan tool, it might pick up the cylinder(s) that are misfiring.

 

I've had that code twice. Once the opti crapped out, another time I burned a plug wire. Check your wires first, then start troubleshooting the rest of the ignition system.

 

Cylinder 3 had a pending code, but never came on. Is that the second plug back on the driver side?

I'm going to swap wires and check the plug for that one.

 

Yes.