Hey Guys,

I am in the process of trying to sell my Evo IX SE.

Recently I've been getting a CEL that read P0300 Random Multiple Cylinder Misfire. I'm not exactly sure what is causing this. I've done a number of things to troubleshoot - all to no avail. Each person that has contacted me with interest in the car I have made aware of this issue.

Here's a quick list of what I've done to try to figure out/fix this problem:

-Ran two bottles of SeaFoam and Lucas Injector cleaner through the car to ensure that the injectors were not clogged.

-Ensured that the spark plugs were not cracked and properly gapped to around 0.22 - 0.24 (Currently am running Denso IKH22 Evo Plugs which I believe are from the dealer.)

-Completely replaced the boots and wires

-Ruled out coil packs being the issue (switched coil packs with a set from a properly functioning Evo but the car still threw the P0300 code)

-Completely disassembled the throttle body cleaning both that and the idle speed sensor

-Thoroughly cleaned the MAF

-Replaced the MAF with a known, working MAF which the car still threw the P0300 code



Some interesting things to note:

-When the MAF is unplugged the car idles PERFECTLY without any indication of a miss. When the MAF is plugged in the car's idling is more choppy and you can hear what sounds to be a "miss" if you listen closely.

-The car does not drive like his has a miss. Under WOT everything seems fine, even regular driving is OK.


I'm at the end of my rope here. I have absolutely no idea what's wrong or even how to fix it. Naturally, nobody is going to want to buy the car when it has a CEL on registering P0300.

Sorry for writing you all a book, any insight you can provide would be greatly appreciated. I've searched these forums high and low and have not found a single shred of evidence pointing to a solution other than having a tuner to just turn the code off.


Thanks again,

Danny

 

Is your car cammed? Cammed cars like to throw that code sometimes

 

Nope, no aftermarket cams. Just stock.

 

It throws the code as soon as you clear it?

 

Yeah, it comes on again within 5 miles of driving.

 

Have you tried leaving the battery disconnected for a while? Its a longshot but id try it anyway

 

silly question, but are you sure you put the spark plug wires and coils to correspond with the correct cylinder?

 

I throw the same code danny. But only when i get on the throttle.

 

Post a screen capture of your ignition and fuel map llarge gaps in between cells and advance idle timing as usual suspects

 

Yup...my uncle is a mechanic and I have had him help me with the P0300 issue as well. His scanner even disabled each injector one at a time to see if one of those was the culprit but all seem fine. We even disconnected the fuel rail with injectors attached to look at the spray patterns....even those turned out fine.

 

Yup because when the boots and wires were first installed they were put in backwards and the car ran terribly.

Coils went in one at a time from another properly functioning Evo sequentially.

 

Mine is on all the time, such a bummer.

 

I'm sorry I'm not following...is this some sort of data logging? I have no idea how to do what your suggesting.

 

He is telling you to read the ecu with Ecuflash and open the tables he listed.

https://www.evolutionm.net/forums/ev...ats-wrong.html

 

after driving for awhile ive learned to throw this code almost on command, for me its driving in 5th gear and anywhere from 3500-4100 rpms i can stutter step the gas pedal and i can count on my cel to turn on every time. and sometimes my car decides to be a punk and i throw the code 6 or 7 times a day for no reason. but i drive an 03 viii and they're notorious for it and each trigger can vary upon each car. my advice is to have a tuner erase the code altogether thats what my plan is.