Random Misfire Code..
 

Hi all,

Been dealing with an annoying problem for the past couple of weeks.

My 2009 Z has been throwing the P0300 code off and on. My buddy works at a Toyota dealership and I brought it in for him to take a look. He said everything looks good, and I can't know what is wrong until I find out what specific cylinder is misfiring?

I have cleared the code a couple of times.. I notice that when I cold start it, and drive for about 20 seconds it will come on every once in a while.

The car starts up, pulls, idles, and drives fine. Can anyone give me some advice, or have any thoughts on what could be wrong?

Thank you!

I had one in my road trip home after installing a turbo kit... Tuner told me to install GTR plugs but I didn't get around to it for about 6 months!!!! Code never resurfaced though. I guess the circumstances were pretty different for me.. but I wasn't boosting when it happened just stopped for gas, then started up and got back on the road and it threw the code so maybe yours was random and won't resurface either?

I am currently having the same issue. Did you ever figure out what it was?

Same issue here after a cold start during fall\winter months.

Just so I can try to help you out Munts, you're saying the misifre only happens when it's on a cold start primarily? And when it runs for a couple of minutes it goes away?

It doesn't go away for me.

I saw a tech when I was at Mercedes work on a 220 chassis that had this similar issue. It turned out to be the solenoid in the fuel injector getting stuck when it was cold out. Once they vehicle ran for a minute the misfire went away.

The Tech who had this car took a heat gun to the fuel injector and hooked up a DMM to the injector. Once the injector started to get warm/hot, the voltage/resistance would change.

The tech replaced the injector and all was well.

Can you get access to data and see what cylinder is misfiring? if not you will need to do a cylinder balance test to isolate what cylinder is misfiring. If all the. Need to start thinking about things they all share, fuel pressure/flow, ignition voltage, maf readings, crank sensor, etc. So first step is it one or all.

Also, the misfire is only when you start it up after sitting for a while, you could have a cracked head. You could pressure test the cooling system.