alright so got a evo 8 and came with the check engine light so went to get the code and it popped up as P0300 i asked the recent owner and he said its been like that for awhile and he used to have somebody delete the code for him but im a bit worried since its a miss fire and the motor can go out on me the spark plugs were done 1,000 miles ago along with the timing belt and gasket i was reading that its mostly the CAI that causes it, i just put seafoam in the gas tank to clean and flush everything out any suggestions what else i can do????? also the cars never been tuned

 

Try get some info in here...random misfire could be anything simple. Check if the plugs aren't burnt, and check if the coils aren't damaged or cracked

https://www.evolutionm.net/forums/ec...300-issue.html

 

It is a kinda common issue for the evo 8. There is a patch to eliminate the P0300 all together. Search for "disable P0300 test". I disabled it years ago and have had no issues since.

If you have a specific cylinder that is miss firing that is something to worry about though.

 

how would i know if a one of the cylinders????

 

If it were to throw a code for a single cylinder misfire it would be p0301 p0302 p0303 or p0304, regarding each cylinder respectively.

 

so i shouldnt be worried about it ??? or should i just switch out the injectors just in case????

 

if it runs fine don't worry about it. as soon as its starting run rough or idle rough then you should really fix it.

 

well im planning to tune it on thursday so maybe he will be able to help me out a bit on the issue
thank you everybody for the suggestions!

 

I drive the same year car as the OP and my car (or any early VIII) will run rough when the p0300 code is thrown. This is something the engine computer is doing. So, running rough while driving is not diagnostic.

 

I just want to feel confortable driving the car and not worried somethng is gonna blow especially the engine

 

The nearest Mitsubishi dealer is 100 miles East of me or, if going the other direction, 400 miles West. Well, back when my car was new, I was going West a lot because I was dating a lady who lived close to that 400 miles West dealership. Without fail, I'd get to the point in the trip where it would be about a 250 mile tow in either direction to reach a dealership and the CE light would come on. The engine would run like it was on 2 or 3 cylinders and I figured I was about to be stranded each time it happened.

First I got a code reader, discovered the p0300 code, and found that if I erased it the car would be okay for another fifty miles. So, I'd have to stop and erase the code 3 to 5 times each trip. This got to be old. Then I heard about the Creader. This is a little cheap code reader that, when plugged in, reads the codes and erases them in one step. Also, and this was the good part, leave it in the socket and never get a code again – any code.

Finally, with the car becoming “Mature” I figured it wasn't such a good idea to have all codes shut off because other things were probably going to fail I needed to know about. So, I went ahead and did the p0300 fix to the ECU programming.

When the Evo 9 was about to come out I was amused to read that the maker was making certain changes to the drive train. So, I thought, the p0300 problem is finally being dealt with. Sorry, no fix for 8 owners from the dealership.

 

Mitsu did offer two rom updates 0014 and 0015 to TRY and combat the issue. Worked for some not for others.

At this point disabling the P0300 code routine is the easiest way to never see the code again.

 

[QUOTE=gsrboi80;10573649]Mitsu did offer two rom updates 0014 and 0015 to TRY and combat the issue. Worked for some not for others.

Tried that - no change. But, this is my experience. Maybe it did help some owners.

 

If you disable the code in one of the ecu patches you can download you will be fine. It has something to do with drivetrain vibrations in 5th gear. It is just a noisy gear.