I got the random misfire code today and took my car to the dealership. They told me this was due to the fact that i have an aftermarked exhaust with the mechanical o2 sensor fix. Is this correct or are they just not want to work on my car? I tried to search couldn't find anything relevant to this thanks.

 

happens to most people. just clear it and go in with life, it will show up down the road at random intervals.

 

The rear O2 sensor does not have anything to do with the code.

DTC P0300: Random/Multiple Cylinder Misfire Detected

This code is very common with the EVO. I belive Dynoflash or someone offers a flash to fix it. I am not sure if mitsu has a flash to fix it or not. Or if you have other mods it could be causing it but a turboback really won't do that.

Ben

 

i think i got, if not the same, a similar code ...(P1300) err sumthin... I was gonna change out my spark plugs, would that help?.... thanx in advance-bRaVo

 

the p0300 code can be caused by almost anything its happened to me numerous times. I work at emissions here in washington, and its real common. Can be a spakr plug not firing perfect everytime and it will come on, not a big deal. Clear it go through ur drive cycle and wait.
The p1300 code is different, it not emission s related, go to google and type in obd 2 codes and it will tell u exactly what it mean... if anyone has emissions questions let me know i can answer most of em'

 

I have BAD Random misfire problem ALL the TIME on the highway. Usually at 75mph and 82mph. Had dealership Pull/Clear code. Upon dealers suggestion I replaced pluggs, and didnt fix. They they said to replace entire ignition system including coils, boots, and wires... still didnt fix. ($411.00 later...dont care about lost money but just want freaking problem fixed!)

Happened out of the blue... I haven't changed mods, or tuning in months. But happens now every day on the highway every 3 to 5 minutes or more.

FREAKING ANNOYING.


Help!

Mods include:
HKS Intake, d-pipe, exhaust
Ultimate racing cat delete pipe w/ special "no check engin light" bung
PWR intercooler
XS Engeneering IC Piping
Stereo system w/ upgraded stinger battery (in trunk) w/ 0 ga wire to the front, and stinger cap (had for a year with no problems)
APEXi SAFC II w/ modified buscher map (more conservative, no fuel correction happening when misfire is occuring)
Megan racing exhaust manifold
21psi when running hard (like next to no boost crusing on highway when problem happens)
Bunch of other body, trans, and suspension mods, but not related to what is causing problem.

 

There's a huge discussion on this forum about this problem. I had this P0300 code on my old VIII. From what I understand, it has something to do with the sensitivity of the CAS. It just started one day while driving. I went and had it flashed 2x at 2 different dealerships but did not fix it. The flash from the dealearship is suppose to make the CAS less sensitive. In my case it never worked. There are some EVO's out there that are just dealing with it. I do agree with genimport, in that, it's very annoying especially while cruising.

I also had the ATS twin carbon clutch which didn't help with the vibration dampening.

My suggestion is go to the dealership and have them flash for the P0300 error code and hope it works. If it doesn't, my only other suggestion is to go stand alone.

Oh, and yeah the creader also works.

 

buy a creader it will kep the code clear!
its nothing dont pay attention to it!

 

If just a simple check engine light was the problem I would not have posted "I have BAD Random misfire problem"... My 03 EVO shakes violently and loses all power repeatidly all the time on the highway.

And yes it is a big deal to have that code in the ecu because from what the factory trained EVO rep at the dealer told me "when a check engine light fires form this code the car automatically pulls timing (i.e. reduces power output)"

To Parrothead's point yes I did do the factory ecu reflash "fix" first but to no avail. (forgot to mention above)

I am looking into having Jester Tuning do a complete reflash (to see if that can cure it) If he doesn't think so I am open to suggestions. I am begining to feel like I need to go AEM Stand alone w/ custom dyno tuning.

Anyone?

 

I'm having the exact same problem, at around 4 to 5000 rpms I'm getting fuel cut or misfire (not sure). And CEL comes on and error code of p0300. I can not get this problem to go away. I've put in nology wires and colder plugs to try to fix it , but nada. I'm starting to look at AEM EMS. There is a place in denver that will put it in for you and tune it for $2100.

 

The dealership reflashed with the updated software that is supposed to take care of the problem. Lets see how long it lasts.

 

Spooln... You may just want to consider that reflash a waste of time... I haven't met one person that it worked for.