I used to get the P0300 code and the rear to front O2 code (difference in voltage) when I ran my reflash.

Instead of disabling the code in the ECU, I opted to fix the actual problem that was causing the "multiple cylinder misfire" code... For me the issue was the ECU flash was done like crap. The car would break up in part throttle in multiple gears.Obviously if it was breaking up, the car was not tuned properly for part throttle. (was not a spark related issue) The obvious bad tune, would cause the O2 sensor to attempt to scale the Fuel trims under part throttle, thus trowing the secondary O2 code.

Instead of "deleting" codes, how come no one is fixing the actual problems?


My car now runs fine, and does not throw any codes and all readiness codes set.It passes NJ inspection with 880cc injectors, GT30 turbo kit and no cat.


I suggest fixing the issue, instead of throwing a fix at it. And Im not trying to rain on anyones parade, but if the ECU is detecting a misfire code, it is most likely because there is a misfire present. It could be under part load, or warm up and would not be incredibly noticible. I know I was seeing AFR's fluctuating from 10.0-18.5 under part throttle on my reflash.

 

I think you're looking at this wrong. This code fix is for people getting false CEL's. Personally I have an aggressive cam combo and the choppy idle triggers the p0300. The ECU thinks there is a misfire. There is no misfire. The tune and my tuner (razorlab aka Bryan@GST) are both excellent. The ECU just isn't programmed to manage aftermarket cams at normal idle speeds and I'm not interested in tricking it into compliance with a 1200 RPM idle. Maybe others have different reasons for using this fix but for me it's about a FALSE dummy light.

 

Well that makes more sense if you have really aggressive cams. However if you look at the AFR's at idle on aggressive cams, you will see some drastic AFR fluctuations. This actually is causing a slight misfire/choppy idle. Like i said, my car did the same exact thing, misfire codes and choppy idle from cams. I went to speed density, and the idles around 13.9-14.4 at 800-900rpms and no misfires.

The more aggressive the cam, the less vacume it produces at idle, thus less Air and fuel being sucked in at idle to ignite. Thus the misfire code.


Good luck let me know how that works for you.

 

Same with me, I got the 272/264 cam combo. So the idle sucks *****. Either way, I still need to know how to either turn off the code from coming up or fix the tune. But doing a full log on my car right now is sort of impossible due to the snow.

Again, how do I open up the rom to add the string to get it fixed. What program should I use?

 

You said your using ecuflash 1.4 right? The perphiary (sp?) definitions are already there. Just look at the first post and see which one you need to turn off. Make sure your ecuflash is in developer mode.

 

fusionevo...open the ROM file with notepad.

 

That was the issue... the rom file I was opening was the rom that I loaded to my ecu. Not the proper XML file. The one I needed help on finding was the evo7base.xml file. I didn't know it was that one. I found out through openecu.org. I'm good now. Thanx though.

 

I think there is a description of the location of the files in the "How To Tune and Evo" Sticky. If you are using XP, its pretty easy to make the changes. Vista is much harder because permissions are much more strict.

 

Yeah, Vista is a pain in the ***. I had to save the file to my desktop and then move it to the right folder. Now I have a question that I'm not too sure about, I've read along the posts that you can change the ROM type, ie: 94170008(my cars) to another evo8 ROM such as the 94170014/15 or what not (as long as the immobilizer code is changed to the on from my ROM). Is that true?
If so, then I would have to transfer the tune to the new ROM, right?


I'm sorry I'm full of questions, just that I'm new to the tuning process and I'm still trying to learn. Thanx

 

I just curious, has anyone set their target AFR at idle a bit richer to say like 13.5???Just curious to see if this works, I know it did on the Nissan 350Z for the p300 codes.

 

I tried it with no success since 99% of my p0300 problem was on a light load (not idle) and under 20% throttle.

 

Ahh, I see..The Nissans from the factory would have a little "pop" or "burp" noticable at idle. The dealers all said it was normal, which I knew it was not, since it triggered a p0300 and lean idle code all the time. When we would tune the cars on the UTEC's we were able to add some fuel at idle and eliminate the code.

If your getting it at part throttle your probably hitting a laen or rich spot in the map.What is your AFR's when this occurs? Have you checked this? This was the exact same thing I would get on my Evo on the reflash under part load.Since I put in the Fcon, and properly tuned it, my car does not throw a single code.

I am curious to see if adding some fuel to idle and the poits where it is misfiring, would solve the problem. You would be surprised what a few breathing mods do to the mapping in the ECU for dirvability.

 

When the car is chucking the p0300 it's in closed loop, so the ECU is actively controlling the AFR's. The P0300 typically happened with large jumps in timing, and even after smoothing those values, you only reduce the tendancy.

In my case, I suspect that it's the 5th gear syncro assembly. issued a TSB stating that under light loads it throws harmonics in the 6khz range, the same range as the knock sensor detects knock....

 

Please confirm if i am doing it correctly. thanks. i have the ecuflash v1.40.2178. this release has the periphery tables already. so to disable the P0300 test i have to change the periphery2 hex value from "EFDF" to "EFCF" then set bit 4 & 5 of periphery2 to 0.

 

Changing the hex or changing the bit values does exactly the same thing, so only the hex or the bits need to be changed.