Just wanted to put this out there for thought, I guess.

I was on the way home from Buschur this afternoon - no work done today, just visiting and dropping off some photos from the shootout - and a little over halfway home while cruising in 5th @ around 75-80 I got an SES light. Almost same exact conditions as the last time that it threw a confirmed P0300 code. Last time this happened was a little over a year ago. The ECU threw the code and my local dealer at the time did the reflash and it took care of the problem for about 3 months. Then again - highway cruising, part throttle and BOING P0300. This time they swapped the #3 and #4 injectors around to determine if there was a problem there..... and the code never came back - until now.

I just got a custom dynoflash about 2 weeks ago and the cars been running fantastic. Added the forge MBC, Helix downpipe and its been great - very smooth and making good power. I dont know that the flash or MBC has anything to do with this - I kinda doubt it, but I wonder why I'm getting a code again.

Perhaps I should have tried to take it to the dealer and see what the code is, but once I got home, I pulled the negative terminal on the battery for about 10 seconds to see if the SES would go away. and its gone now. I hope its stays gone.

So anyway - not sure what exactly it is, but the conditions under which the SES came on sure smells like that P0300 creeping back up.

Anyone have any thoughts on this?

Warrtalon - would you have any advice? thanks!

 

I know that the casting on the Tranny can cause the P300 code on 03's and some 04's.

 

Casting on the tranny? I don't follow...

I had the P0300 once about 2 months after I bought my Evo. The dealer replaced a fouled plug and I didn't get another SES for over a year. Fast foward to about 4 months ago and I am getting the light 3 times in a 2 week period. I take the car back to Mitsu and they reflash my ECU. This was done in April 06 and since the reflash I've had the P0300 code come back 7 times.

Each time it happens the car hesitates for a moment and the light pops on, then all goes back to normal. I purchased an Actron OBD II scan tool a long time ago just so I can save myself the trip to the dealer.

Got the code again two nights ago and talked to Mitsu about it. The REFUSE to even diagnose at the car until I "Return it completely back to OEM specs". Of course all my mods are Air or Fuel based changes, not ignition. But they don't care here at Leith Fayetteville, all they give a damn about is selling cars and saving money. I mean hell, all I wanted from them was an explanation why the same code keeps coming up.

 

I am tempted to get a scan tool for "just in case". Although I am not sure if I should actually take the car in or not. I dont really want to have to go through the trouble of Mitsu flashing the ecu and thereby overwriting my custom flash by Al.

As I understand it, in most cases, the random misfire code is caused by harmonics or vibrations that are sent up from the transmission and they trigger the misfire sensor.
I could be wrong, so dont quote me on that. Hopefully someone else who knows more that I do can clarify or deny this.

Is the P0300 code one that we can safely ignore? Thats what I'd really like to know. Since it is such a common problem on the '03 and some '04's, it sounds like a minor system problem rather than something really troubling.

One more thing that I'd like to note - I thought that the ECU would go into a "limp" mode and cut down boost or something like that once there was an SES warning? I didnt notice any difference yesterday with the boost levels or the AFR. Of course - that could be because I'm no longer using the factory boost solenoid... (?)

 

Ive had a p0300 code 8 time since owning the car. No pattern to the timing; the shortest time between throwing the code has been 2 days and the longest 8 months. My Dynoflash seemed to help though.

 

I run the SMART Xede and with that installation we have the C-Reader. I leave that plugged in all the time since with Xede we are constantly making timing adjustments -- that too can cause the P300 code.

Yes, I believe this is a code we can safely ignore -- I get it a few times even on my 05 but I have yet to see it affect performance on the car.