P0300 random cyl misfire
 

Has anyone had a P0300 DTC and if so what was the cause...
Thanks

Yes I did...
 

It was because the spark plug grenaded...

Jaden

Interesting I will pull mine tomorrow...... It has only done it once but who knows.

Oh you'd know...
 

I say it was because the spark plug grenaded but it was the precursor to it grenading, the cylinder wasn't really firing at all once it failed completely.


Jaden

Are your afr ok, not running lean.
no high ltft

check earth connections
is the di injection computer securly grounded its grounded via mounting bolts

Just threw that code today afr was not reading lean. Cel popped on and off for like 1 min while I was driving then went away on its own. Any ideas what could cause this or what I should look for?

There are approximately 4,593 things that can cause a P0300. We need more to work with.

You can pull everything everywhere and do a general inspection for anything broken. Check for vacuum leaks. But don't start throwing parts at a P0300, you won't fix it but you will spend a lot of money replacing good working OEM parts for shit aftermarket parts.

Mine is at the dealer now for P0301 and P0300; running rough and stalling out at low RPM. The first theory was the coil pack for cylinder 1. Replacing it didn't fix it. The spark plugs were replaced about a month ago. They checked a bunch of other things and couldn't find the cause. They kicked it up to Toyota and after a week got back a new theory; cylinder 1 exhaust valve spring is weak and/or damaged. They are about to start tearing down the engine to find out and maybe fix. So, yeah, it seems it can be really hard to figure out the cause. I'm not sure they've figured out mine yet.

This is the one I had problems with - lost one of the mounting bolts to the underbody monster and didn't think it was a big deal... turns out it is.

Figured out what the problem was?