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Hey guys I have a stock 2008 Infiniti G37s 6mt, I've read everywhere on the forum and online on what could be causing this, but i got my car throwing a code for P0300 random cylinder misfire. I already replaced the spark plugs, seemed to make it worse the following weeks (I could actually start feeling it, still only misfires when cold though) until I found out the coolant hose from my throttle body was leaking onto my #3 cylinder ignition coil, I replaced the damaged coil and fixed that coolant leak, while doing this I noticed I small crack on one of my intake hoses, replaced it with the mishimoto intake tubes to eliminate that vacuum leak, it seemed to have fixed the issue, until a day later that same code pops back up! I've already replaced my spark plugs, coils, and I'm sure there arent anymore vacuum leaks, I've tried using additives to clean up my fuel injectors, I dont want to be spending any more money on parts I dont need, what could be the issue with this?? The car drives fine and I dont feel any misfire,
PS. The car drives fine and I dont feel it misfiring whatsoever, idle is just a little high due to the ECU raising it because of the code, it goes back down after clearing the code. And it only happens to trigger the code on cold starts when I start it up first thing in the morning around 1-30 misfires on random cylinders then the misfire counter stops rising
How’s your alphas look? (Short term fuel trim for generic scan tools) look at bank 1 and 2 when warm they should be between 93% and about 103% lower The number the richer it is. But in your case it seems that it’s jumping around. I’d bet it’s running lean 115-130% check the back of your plenum there are some evap hoses coming from your purge valve that tend to crack after time and cause your concern.
Hey sorry I didnt realize I got a reply on this thread, but I'm getting %99.219 on both banks. I took a close look at my plenum and I havent seen any types of crack or anything that would cause a leak.. I also took a closer look at which cylinders were misfiring, it seems like they're mostly misfiring on cylinders 1 3 & 5 I'm getting worried my head gasket on that side of the engine is starting to go. Could you please tell me otherwise lol, the car still runs perfectly fine though and the engine is running strong with no signs of performance loss.. I'm so confused.
i just signed up here so that i could respond to this thread. it’s not letting me start a pm with you, probably because it’s a new account. could you try PMing me first?
i just signed up here so that i could respond to this thread. it’s not letting me start a pm with you, probably because it’s a new account. could you try PMing me first?
it’s not letting me PM you. Call me on my shop line 4158304008
Just post the fix on the forum, or don't bother with the forum at all. Otherwise, what's the point? It's a forum.
Like I said above, there is no one fix. My fix is to data log the car with an ecutek flashed ECU that I can provide as needed. I perform an in depth analysis of engine behavior to determine if there are fuel pressure issues, spark/ignition issues, or other related problems that can trigger the code. There are also firmware updates and intake/exhaust leak issues. Again, it's not a one size fits all solution, diagnosis is required - that is my fix.
