p0300 random misfire in all cylinders help!

[TsiJohn333]

i have the famous P0300 - Random misfire in all cylinders code.

To start off, it only does this at random times like when driving. It will misfire in all cylinders for about 2 seconds or at times 5 minutes but no longer than that. When it does happen though, I notice that my wideband is reading fully lean, even when i gas it. I have to floor the car when it does it in order for it to go away.

I am lead to believe that it might be a cam angel sensor? or power resistor box? I'm really not sure on this.

I don't think it would be my coil packs considering i have coil on plugs and the odds off all four of them going out randomly are slim to none. I did however replace all my injectors with new ones and replaced my fuel pump thinking it was something fuel related but still does the same thing.

My current mods are:
Evo III big 16g turbo
coil-on-plugs
evo injectors and fuel pump
3 inch turbo back with cat delete
big fmic
SAFC2
aem wideband

Thanks in advance,
John

 

[GRAVEDIGGER]

Have you looked at the plugs, or checked the gap yet? Might be a good idea to just change them and see if that helps any.

 

[TsiJohn333]

Thank you for the reply. i already checked that today and replaced them with all new ngk spark plugs and and made sure the gap was .28. It still did the missfire thing again today. =(

its really getting annoying now

I read a forum earlier this morning that it could be the resistor pack for the injectors. Could this possibly cause the missfire? and how can i test it and where is it located?

Just an update: its constantly misfiring now. I just replaced my spark plugs, power transistor pack and my CAS with no luck. Could it be a CPS?

 

[squeak104]

Don't happen to have a lightweight flywheel do you? I had two cars that would create that misfire because I suck at centering the flywheel without a dowel in the crank. Once I put a dowel pin in the crank for the flywheel it cured the problem on both cars.

 

[TsiJohn333]

I do not. i have an automatic gst with a stock drivetrain.

 

[genegoesfast]

Are you running a stock cas? If not is it a 1g cas by any chance?

 

[TsiJohn333]

Yeah its a stock cas. i went out and bought a new one thinking it was that but no luck =( This car is driving me nuts!

 

[TsiJohn333]

i honestly think its my cps. where is it located and is it hard to change?

 

[snowborder714]

You can see the CPS in this picture.

 

[TsiJohn333]

Thank you Brian for that info! I finally figured out the problem though!

Since i have coil on plugs, each of them are wired together to fire in a certain order BUT if one goes, then it would not be able to complete the circuit in which they are suppose to fire causing each and everyone of them to misfire. i figured out by tapping on each coil to see if it would stop the misfire. When i tapped cylinder number 3 coil, it went away. I replaced the coil, and shes driving like a champ. thank you everyone who has helped me!